Fix RuleBuilder remoteable actions running in the local pool.

This CL fixes a bug with RuleBuilder's handling of remoteable actions.
It adds a new type of pool to identify remoteable rules by the android
module context. The pool is then set to nil to actually run actions at
NINJA_REMOTE_NUM_JOBS parallelism.

Test: built aosp crosshatch userdebug
Change-Id: I29452f6fc7a161b94189731e3e3cc1f34907b80c
diff --git a/android/defs.go b/android/defs.go
index 5c815e6..4552224 100644
--- a/android/defs.go
+++ b/android/defs.go
@@ -100,6 +100,9 @@
 	// Used only when USE_GOMA=true is set, to restrict non-goma jobs to the local parallelism value
 	localPool = blueprint.NewBuiltinPool("local_pool")
 
+	// Used only by RuleBuilder to identify remoteable rules. Does not actually get created in ninja.
+	remotePool = blueprint.NewBuiltinPool("remote_pool")
+
 	// Used for processes that need significant RAM to ensure there are not too many running in parallel.
 	highmemPool = blueprint.NewBuiltinPool("highmem_pool")
 )