BoehmGCStackAllocator: ignore stack protection page

This fixes a crash that looks like:

```
Thread 1 "nix-build" received signal SIGSEGV, Segmentation fault.
0x00007ffff7ad22a0 in GC_push_all_eager () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
(gdb) bt
0  0x00007ffff7ad22a0 in GC_push_all_eager () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
1  0x00007ffff7adeefb in GC_push_all_stacks () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
2  0x00007ffff7ad5ac7 in GC_mark_some () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
3  0x00007ffff7ad77bd in GC_stopped_mark () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
4  0x00007ffff7adbe3a in GC_try_to_collect_inner.part.0 () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
5  0x00007ffff7adc2a2 in GC_collect_or_expand () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
6  0x00007ffff7adc4f8 in GC_allocobj () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
7  0x00007ffff7adc88f in GC_generic_malloc_inner () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
8  0x00007ffff7ae1a04 in GC_generic_malloc_many () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
9  0x00007ffff7ae1c72 in GC_malloc_kind () from /nix/store/p1z58l18klf88iijpd0qi8yd2n9lhlk4-boehm-gc-8.0.4/lib/libgc.so.1
10 0x00007ffff7e003d6 in nix::EvalState::allocValue() () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
11 0x00007ffff7e04b9c in nix::EvalState::callPrimOp(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
12 0x00007ffff7e0a773 in nix::EvalState::callFunction(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
13 0x00007ffff7e0a91d in nix::ExprApp::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
14 0x00007ffff7e0a8f8 in nix::ExprApp::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
15 0x00007ffff7e0e0e8 in nix::ExprOpNEq::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
16 0x00007ffff7e0d708 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
17 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
18 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
19 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
20 0x00007ffff7e0d695 in nix::ExprOpOr::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
21 0x00007ffff7e09e19 in nix::ExprOpNot::eval(nix::EvalState&, nix::Env&, nix::Value&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
22 0x00007ffff7e0a792 in nix::EvalState::callFunction(nix::Value&, nix::Value&, nix::Value&, nix::Pos const&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
23 0x00007ffff7e8cba0 in nix::addPath(nix::EvalState&, nix::Pos const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Value*, nix::FileIngestionMethod, std::optional<nix::Hash>, nix::Value&)::{lambda(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)#1}::operator()(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixexpr.so
24 0x00007ffff752e6f9 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
25 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
26 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
27 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
28 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
29 0x00007ffff752e8e2 in nix::dump(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, nix::Sink&, std::function<bool (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)>&) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
30 0x00007ffff757f8c0 in void boost::context::detail::fiber_entry<boost::context::detail::fiber_record<boost::context::fiber, nix::VirtualStackAllocator, boost::coroutines2::detail::pull_coroutine<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::control_block::control_block<nix::VirtualStackAllocator, nix::sinkToSource(std::function<void (nix::Sink&)>, std::function<void ()>)::SinkToSource::read(char*, unsigned long)::{lambda(boost::coroutines2::detail::push_coroutine<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&)#1}>(boost::context::preallocated, nix::VirtualStackAllocator&&, nix::sinkToSource(std::function<void (nix::Sink&)>, std::function<void ()>)::SinkToSource::read(char*, unsigned long)::{lambda(boost::coroutines2::detail::push_coroutine<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&)#1}&&)::{lambda(boost::context::fiber&&)#1}> >(boost::context::detail::transfer_t) () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libnixutil.so
31 0x00007ffff6f331ef in make_fcontext () from /nix/store/hzdzcv9d3bc8rlsaphh7x54zsf0x8nx6-nix-2.4pre20210601_5985b8b/lib/libboost_context.so.1.69.0
32 0x0000000000000000 in ?? ()
```

0 files changed, 0 insertions, 0 deletions