In preparation for the deprecation of `stdenv.isX`.
These shorthands are not conducive to cross-compilation because they
hide the platforms.
Darwin might get cross-compilation for which the continued usage of `stdenv.isDarwin` will get in the way
One example of why this is bad and especially affects compiler packages
https://www.github.com/NixOS/nixpkgs/pull/343059
There are too many files to go through manually but a treewide should
get users thinking when they see a `hostPlatform.isX` in a place where it
doesn't make sense.
```
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv.is" "stdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv'.is" "stdenv'.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "clangStdenv.is" "clangStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "gccStdenv.is" "gccStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenvNoCC.is" "stdenvNoCC.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "inherit (stdenv) is" "inherit (stdenv.hostPlatform) is"
fd --type f "\.nix" | xargs sd --fixed-strings "buildStdenv.is" "buildStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "effectiveStdenv.is" "effectiveStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "originalStdenv.is" "originalStdenv.hostPlatform.is"
```
Fix wrong header for statfs function.
Use gccStdenv to build with GCC on all systems. GCC is hardcoded in
configure.in, but after setting CC_FOR_BUILD to cc to use Clang, the
build fails anyway when running a post-compilation command:
clang -DLOCALE=LANG_en -DLOCALE_DESC="\"en\"" -DPKGLIBDIR="\"<out>/lib/arj\"" -D_UNIX -g -O2 -o darwin20.6.0/en/rs/arj/arj <objects_files>
: darwin20.6.0/en/rs/arj/arj
./darwin20.6.0/en/rs/tools/join ./darwin20.6.0/en/rs/arj/arj ./darwin20.6.0/en/rs/arjsfxjr/arjsfxjr
JOIN v 1.30 [26/04/2003] Not a part of any binary package!
Copying .. done!
./darwin20.6.0/en/rs/tools/join ./darwin20.6.0/en/rs/arj/arj ./darwin20.6.0/en/rs/arjsfx/arjsfx
JOIN v 1.30 [26/04/2003] Not a part of any binary package!
Copying ... done!
./darwin20.6.0/en/rs/tools/join ./darwin20.6.0/en/rs/arj/arj ./darwin20.6.0/en/rs/arjsfxv/arjsfxv
JOIN v 1.30 [26/04/2003] Not a part of any binary package!
Copying ..... done!
./darwin20.6.0/en/rs/tools/join ./darwin20.6.0/en/rs/arj/arj ./darwin20.6.0/en/rs/sfxstub/sfxstub
JOIN v 1.30 [26/04/2003] Not a part of any binary package!
Copying . done!
rm -f ./darwin20.6.0/en/rs/help.arj
TZ=UTC0 ./darwin20.6.0/en/rs/arj/arj a ./darwin20.6.0/en/rs/help.arj -+ -t1f -2d -e -jm -jh65535 -jt -hdo200506231314 ./resource/en/arj?.txt
ARJ32 v 3.10, Copyright (c) 1998-2004, ARJ Software Russia.
Creating archive : ./darwin20.6.0/en/rs/help.arj
Adding ./resource/en/arjl.txt 37.2%
Adding ./resource/en/arjs.txt 47.3%
Testing arjl.txt OK
Testing arjs.txt OK
2 file(s)
./darwin20.6.0/en/rs/tools/join ./darwin20.6.0/en/rs/arj/arj ./darwin20.6.0/en/rs/help.arj
JOIN v 1.30 [26/04/2003] Not a part of any binary package!
Copying . done!
./darwin20.6.0/en/rs/tools/postproc darwin20.6.0/en/rs/arj/arj
POSTPROC v 1.30 [17/01/2003] Not a part of any binary package!
Patch not found
make[1]: *** [GNUmakefile:398: darwin20.6.0/en/rs/arj/arj] Error 3
