foot: add tests checking the clang compilation to the package

I want to support this in the future. Since I sometimes forget to check
clang compilation when doing a version bump, there has been regression
to this in the past. Let's prevent this by checking compilation with the
default clang version in nixpkgs and the latest clang as well.

pkgs/applications/terminal-emulators/foot/default.nix

@@ -18,6 +18,10 @@
 , pkg-config
 , allowPgo ? true
 , python3  # for PGO
+# for clang stdenv check
+, foot
+, llvmPackages
+, llvmPackages_latest
 }:
 
 let
@@ -140,6 +144,16 @@ stdenv.mkDerivation rec {
     llvm-profdata merge default_*profraw --output=default.profdata
   '';
 
+  passthru.tests = {
+    clang-default-compilation = foot.override {
+      inherit (llvmPackages) stdenv;
+    };
+
+    clang-latest-compilation = foot.override {
+      inherit (llvmPackages_latest) stdenv;
+    };
+  };
+
   meta = with lib; {
     homepage = "https://codeberg.org/dnkl/foot/";
     changelog = "https://codeberg.org/dnkl/foot/releases/tag/${version}";