Materialize the runfiles output manifest as a symlink instead of a co…

…py when building with --nobuild_runfile_links.

Compare with the equivalent code path for --build_runfile_links in SymlinkTreeStrategy#createOutput.

PiperOrigin-RevId: 552457444
Change-Id: I8ae22a15fcdc60395dfe2a112b6dc59e0ed10236

src/main/java/com/google/devtools/build/lib/exec/SymlinkTreeHelper.java

@@ -138,12 +138,13 @@ public void createSymlinks(
 
   /** Copies the input manifest to the output manifest. */
   public void copyManifest() throws ExecException {
-    // Pretend we created the runfiles tree by copying the manifest
+    // Pretend we created the runfiles tree by symlinking the output manifest to the input manifest.
+    Path outputManifest = getOutputManifest();
     try {
       symlinkTreeRoot.createDirectoryAndParents();
-      FileSystemUtils.copyFile(inputManifest, getOutputManifest());
+      outputManifest.createSymbolicLink(inputManifest);
     } catch (IOException e) {
-      throw new EnvironmentalExecException(e, Code.SYMLINK_TREE_MANIFEST_COPY_IO_EXCEPTION);
+      throw new EnvironmentalExecException(e, Code.SYMLINK_TREE_MANIFEST_LINK_IO_EXCEPTION);
     }
   }