Make sure output directory for actool exists before invoking actool

Previously, each "actool" compile action declared an output directory
but didn't create it. Instead, it relied on Bazel to create the
directory before invoking the tool. With a non-remote spawn strategy,
Bazel would implicitly create it for you; but with the remote spawn
strategy, it is not created by the remote worker.

Additionally, this was also against what was documented for
declare_directory, which says that "You must create an action that
generates the directory".

This patches the "actool" wrapper to create an empty directory if one
doesn't exist at the specified output path, to make it works with remote
execution.

#896

RELNOTES: None
PiperOrigin-RevId: 423797086

tools/xctoolrunner/xctoolrunner.py

@@ -212,6 +212,16 @@ def actool(_, toolargs):
 
   xcrunargs += toolargs
 
+  # The argument coming after "--compile" is the output directory. "actool"
+  # expects an directory to exist at that path. Create an empty directory there
+  # if one doesn't exist yet.
+  for idx, arg in enumerate(toolargs):
+    if arg == "--compile":
+      output_dir = toolargs[idx + 1]
+      if not os.path.exists(output_dir):
+        os.makedirs(output_dir)
+      break
+
   # If we are running into problems figuring out "actool" issues, there are a
   # couple of environment variables that may help. Both of the following must be
   # set to work.