swt: fix build with gcc15 and add darwin support

pkgs/by-name/sw/swt/package.nix

@@ -31,7 +31,7 @@ stdenv.mkDerivation (finalAttrs: {
     x86_64-darwin.platform = "cocoa-macosx-x86_64";
     x86_64-darwin.hash = "sha256-Uns3fMoetbZAIrL/N0eVd42/3uygXakDdxpaxf5SWDI=";
     aarch64-darwin.platform = "cocoa-macosx-aarch64";
-    aarch64-darwin.hash = "sha256-Uns3fMoetbZAIrL/N0eVd42/3uygXakDdxpaxf5SWDI";
+    aarch64-darwin.hash = "sha256-jvxmoRFGquYClPgMqWi2ylw26YiGSG5bONnM1PcjlTM=";
   };
   passthru.srcMetadata =
     finalAttrs.passthru.srcMetadataByPlatform.${stdenv.hostPlatform.system} or null;
@@ -47,25 +47,29 @@ stdenv.mkDerivation (finalAttrs: {
       url = "https://archive.eclipse.org/eclipse/downloads/drops4/R-${finalAttrs.fullVersion}/swt-${finalAttrs.version}-${srcMetadata.platform}.zip";
       inherit (srcMetadata) hash;
       stripRoot = false;
-      postFetch = ''
-        mkdir "$unpackDir"
-        cd "$unpackDir"
+      postFetch =
+        # On Linux, extract and use only the sources from src.zip
+        lib.optionalString stdenv.hostPlatform.isLinux ''
+          mkdir "$unpackDir"
+          cd "$unpackDir"
 
-        renamed="$TMPDIR/src.zip"
-        mv -- "$out/src.zip" "$renamed"
-        unpackFile "$renamed"
-        rm -r -- "$out"
+          renamed="$TMPDIR/src.zip"
+          mv -- "$out/src.zip" "$renamed"
+          unpackFile "$renamed"
+          rm -r -- "$out"
 
-        mv -- "$unpackDir" "$out"
-      '';
+          mv -- "$unpackDir" "$out"
+        '';
     };
 
   nativeBuildInputs = [
     jdk
     stripJavaArchivesHook
+  ]
+  ++ lib.optionals stdenv.hostPlatform.isLinux [
     pkg-config
   ];
-  buildInputs = [
+  buildInputs = lib.optionals stdenv.hostPlatform.isLinux [
     gtk3
     libGLU
   ];
@@ -76,14 +80,17 @@ stdenv.mkDerivation (finalAttrs: {
   OUTPUT_DIR = "${placeholder "out"}/lib";
   # GTK4 is not supported yet. See:
   # https://github.com/eclipse-platform/eclipse.platform.swt/issues/652
-  makeFlags = "gtk3";
-  preBuild = ''
+  makeFlags = lib.optionals stdenv.hostPlatform.isLinux [ "gtk3" ];
+
+  NIX_CFLAGS_COMPILE = lib.optionalString stdenv.hostPlatform.isLinux "-std=gnu17";
+  postPatch = lib.optionalString stdenv.hostPlatform.isLinux "substituteInPlace library/make_linux.mak --replace-fail 'CFLAGS += -Werror' ''";
+  preBuild = lib.optionalString stdenv.hostPlatform.isLinux ''
     cd library
     mkdir -p ${finalAttrs.OUTPUT_DIR}
   '';
 
-  # Build the jar
-  postBuild = ''
+  # Build the jar (Linux only, Darwin uses prebuilt)
+  postBuild = lib.optionalString stdenv.hostPlatform.isLinux ''
     cd ../
     mkdir out
     find org/ -name '*.java' -type f -exec javac -encoding utf8 -d out/ {} +
@@ -97,9 +104,27 @@ stdenv.mkDerivation (finalAttrs: {
     runHook preInstall
 
     install -d -- "$out/jars"
+
+  ''
+  # On Darwin, use the prebuilt swt.jar which includes native libraries
+  + lib.optionalString stdenv.hostPlatform.isDarwin ''
+    # Remove signature files to avoid validation errors after stripJavaArchivesHook modifies the jar
+    mkdir -p jar-temp
+    cd jar-temp
+    ${jdk}/bin/jar -xf ../swt.jar
+    rm -f META-INF/*.SF META-INF/*.RSA META-INF/*.DSA
+    ${jdk}/bin/jar -cf "$out/jars/swt.jar" *
+    cd ..
+    rm -rf jar-temp
+
+  ''
+  # On Linux, build from source
+  + lib.optionalString stdenv.hostPlatform.isLinux ''
     install -m 644 -t out -- version.txt
     (cd out && jar -c *) > "$out/jars/swt.jar"
 
+  ''
+  + ''
     runHook postInstall
   '';