Soong: Add BUILD_MODULES build action in soong_ui.

There was one case that did not work:
  1) Create dir in root source tree
  2) Run "m libc"

The build would fail as it was using the mma logic. A separate
one named BUILD_MODULES was added to allow building specific
modules in any directories using the "m" command.

Bug: b/130049705
Test: unit test cases, ran "m libc" in a tmp directory inside
      of the source tree.

Change-Id: I8d23e685a673a311001ee8edd89bd73b662392dd
diff --git a/cmd/soong_ui/main.go b/cmd/soong_ui/main.go
index b909779..b63918f 100644
--- a/cmd/soong_ui/main.go
+++ b/cmd/soong_ui/main.go
@@ -337,7 +337,7 @@
 	}{{
 		name:              "all-modules",
 		description:       "Build action: build from the top of the source tree.",
-		action:            build.BUILD_MODULES_IN_A_DIRECTORY,
+		action:            build.BUILD_MODULES,
 		buildDependencies: true,
 	}, {
 		name:              "modules-in-a-dir-no-deps",