Use the action-scoped tmpdir for temporary files

This is both the correct thing to do, and also makes it much more obvious when
the Assets.car file and Info.plist file are being written to different
directories for reasons of actool being crazy.

--
MOS_MIGRATED_REVID=88853163

src/tools/xcode-common/java/com/google/devtools/build/xcode/zippingoutput/Wrappers.java

@@ -20,6 +20,7 @@
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.nio.file.FileSystem;
 import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -38,14 +39,16 @@ private Wrappers() {
    */
   public static void execute(String[] argsArray, Wrapper wrapper)
       throws IOException, InterruptedException {
+    FileSystem filesystem = FileSystems.getDefault();
     ArgumentsParsing argsParsing = ArgumentsParsing.parse(
-        FileSystems.getDefault(), argsArray, wrapper.name(), wrapper.subtoolName());
+        filesystem, argsArray, wrapper.name(), wrapper.subtoolName());
     for (String error : argsParsing.error().asSet()) {
       System.err.printf(error);
       System.exit(1);
     }
+    Path tempDir = getTempDir(filesystem);
     for (Arguments args : argsParsing.arguments().asSet()) {
-      Path outputDir = Files.createTempDirectory("ZippingOutput");
+      Path outputDir = Files.createTempDirectory(tempDir, "ZippingOutput");
       Path rootedOutputDir = outputDir.resolve(args.bundleRoot());
       Files.createDirectories(
           wrapper.outputDirectoryMustExist() ? rootedOutputDir : rootedOutputDir.getParent());
@@ -64,4 +67,12 @@ public static void execute(String[] argsArray, Wrapper wrapper)
       }
     }
   }
+
+  private static Path getTempDir(FileSystem filesystem) {
+    String tempDir = System.getenv("TMPDIR");
+    if (tempDir == null) {
+      tempDir = "/tmp";
+    }
+    return filesystem.getPath(tempDir);
+  }
 }