packaging: rename nixexpr -> lixexpr and so on

This breaks downstreams linking to us on purpose to make sure that if
someone is linking to Lix they're doing it on purpose and crucially not
mixing up Nix and Lix versions in compatibility code.

We still need to fix the internal includes to follow the same schema so
we can drop the single-level include system entirely. However, this
requires a little more effort.

This adds pkg-config for libfetchers and config.h.

Migration path:
expr.hh      -> lix/libexpr/expr.hh
nix/config.h -> lix/config.h

To apply this migration automatically, remove all `<nix/>` from
includes, so: `#include <nix/expr.hh>` -> `#include <expr.hh>`. Then,
the correct paths will be resolved from the tangled mess, and the
clang-tidy automated fix will work.

Then run the following for out of tree projects:

```
lix_root=$HOME/lix
(cd $lix_root/clang-tidy && nix develop -c 'meson setup build && ninja -C build')
run-clang-tidy -checks='-*,lix-fixincludes' -load=$lix_root/clang-tidy/build/liblix-clang-tidy.so -p build/ -fix src
```

Related: https://git.lix.systems/lix-project/nix-eval-jobs/pulls/5
Fixes: https://git.lix.systems/lix-project/lix/issues/279
Change-Id: I7498e903afa6850a731ef8ce77a70da6b2b46966

1 files changed, 1 insertions, 1 deletions

diff --git a/meson/cleanup-install.bash b/meson/cleanup-install.bash
index 3e229cbc6..928edc74a 100755
--- a/meson/cleanup-install.bash
+++ b/meson/cleanup-install.bash
@@ -47,4 +47,4 @@ fi
 
 # Intentionally not using -f.
 # If these files don't exist then our assumptions have been violated and we should fail.
-rm -v "$includedir/nix/parser-tab.cc" "$includedir/nix/lexer-tab.cc"
+rm -v "$includedir/lix/libexpr/parser-tab.cc" "$includedir/lix/libexpr/lexer-tab.cc"