Without this PR, unlike `RUST_LIB_BACKTRACE=1 cargo run` you won't
get line numbers in backtraces from binaries built with:
```
nix build -f Cargo.nix --arg release false
```
This PR fixes that.
In https://github.com/NixOS/nixpkgs/pull/209870 I tried to unify the
treatment of clang and gcc in cc-wrapper as much as possible.
However it appears that I went too far.
Clang requires -isystem flags in order to be able to find gcc's
libstdc++. Gcc does not need these flags. If they are added,
gfortran will get confused:
https://github.com/NixOS/nixpkgs/pull/209870#issuecomment-1500550903
This commit deunifies the chunk of code that adds the -isystem
flags, and explains why this chunk applies only to clang.
The build.rs script shipped with evdev-sys attempts to detect cross
compilation and uses a completely different codepath which does a
`git fetch` inside the build script. This doesn't work in nixpkgs.
This PR adds a `touch libevdev/.git` to trick the `build.rs` into
thinking that it is not necessary to do a `git fetch`.
Thanks to @figsoda for finding this more-elegant solution to the
problem (my original solution needed to patch `build.rs`):
https://github.com/NixOS/nixpkgs/pull/224893#pullrequestreview-1373809617
Tested on:
- [x] `aarch64-linux` (cross from `x86_64-linux`)
AFAIK this doesn't have a noticable effect for typical
Linux executables, but will avoid setting the timestamp
inside the file for Windows executables to the build
date.
Without this change, the `--os` and `--arch` switches are disregarded
for operations involving `skopeo inspect` invocations. This means that,
for example, one cannot fetch Linux images while on macOS.
Unlike most other trivial builders, writeShellApplication has a
relatively heavy checkphase that invokes shellcheck. On my system,
a small writeShellApplication takes over 1 second to build.
This PR allows substitutions and stops preferring local builds for
writeShellApplication.
The Nix-driven bootstrap of gcc resulted in some changes to the
structure of the `libgccjit` outpaths, and also added an additional
output (`libgcc`) to `gcc`.
This commit makes the corresponding changes in the `emacs`
derivation in order to not break emacs.
Emacs is the only user of `libgccjit` in nixpkgs at the moment.
