{libedit,sharutils}: move env vars to `env.*`

Closes https://github.com/NixOS/nixpkgs/issues/273746
See https://github.com/NixOS/nixpkgs/pull/217206

Co-authored-by: Weijia Wang <[e-mail]>

pkgs/development/libraries/libedit/default.nix

···
   # There is a DR to fix this issue with Clang which is not merged
   # yet.
   # https://reviews.llvm.org/D137043
-  NIX_CFLAGS_COMPILE = lib.optional
-    (stdenv.targetPlatform.isMusl && stdenv.cc.isClang)
-    "-D__STDC_ISO_10646__=201103L";
+  env.NIX_CFLAGS_COMPILE =
+    lib.optionalString (stdenv.targetPlatform.isMusl && stdenv.cc.isClang)
+      "-D__STDC_ISO_10646__=201103L";
 
   patches = [ ./01-cygwin.patch ];
 

pkgs/tools/archivers/sharutils/default.nix

···
     '';
 
   # Workaround to fix the static build on macOS.
-  NIX_CFLAGS_COMPILE = "-Wno-implicit-function-declaration";
+  env.NIX_CFLAGS_COMPILE = "-Wno-implicit-function-declaration";
 
   doCheck = true;