ponyc: Fixes code generation to use generic arch, not native (#491562)

pkgs/by-name/po/ponyc/package.nix

@@ -99,6 +99,20 @@ stdenv.mkDerivation rec {
         --replace-fail "https://github.com/google/googletest/releases/download/v$googletestRev/googletest-$googletestRev.tar.gz" "$NIX_BUILD_TOP/deps/googletest-$googletestRev.tar"
   '';
 
+  # We do not concern ourselves with darwin as the ponyc compiler
+  # has logic which overrides this environmental variable in this
+  # case.
+  env.arch =
+    if stdenv.hostPlatform.isx86_64 then
+      "x86-64"
+    else if stdenv.hostPlatform.isAarch64 then
+      "armv8-a"
+    else
+      lib.warn ''
+        architecture '${stdenv.hostPlatform.system}' compiles with native optimizations,
+        this may result in crashes on incompatible CPUs!
+      '' "native";
+
   preBuild = ''
     extraFlags=(build_flags=-j$NIX_BUILD_CORES)
   ''