fix(cargo-pgrx): disable sccache on Darwin

Author: yvan-sraka

nix/cargo-pgrx/buildPgrxExtension.nix

@@ -165,15 +165,21 @@ let
     buildPhase = ''
       runHook preBuild
 
-
-      if [[ -d "/nix/var/cache/sccache" && -w "/nix/var/cache/sccache" ]]; then
-        echo "sccache: cache directory available, enabling"
-        export RUSTC_WRAPPER="${sccache}/bin/sccache"
-        export SCCACHE_DIR="/nix/var/cache/sccache"
-        export SCCACHE_CACHE_SIZE="50G"
-      else
-        echo "sccache: cache directory not available, skipping"
-      fi
+      ${lib.optionalString (!stdenv.hostPlatform.isDarwin) ''
+        if [[ -d "/nix/var/cache/sccache" && -w "/nix/var/cache/sccache" ]]; then
+          # Test if sccache can actually write to the directory (sandbox check)
+          if touch "/nix/var/cache/sccache/.test" 2>/dev/null && rm -f "/nix/var/cache/sccache/.test" 2>/dev/null; then
+            echo "sccache: cache directory available and writable in sandbox, enabling"
+            export RUSTC_WRAPPER="${sccache}/bin/sccache"
+            export SCCACHE_DIR="/nix/var/cache/sccache"
+            export SCCACHE_CACHE_SIZE="50G"
+          else
+            echo "sccache: cache directory not accessible in sandbox (needs extra-sandbox-paths configuration), skipping"
+          fi
+        else
+          echo "sccache: cache directory not available, skipping"
+        fi
+      ''}
 
       echo "Executing cargo-pgrx buildPhase"
       ${preBuildAndTest}