Specify module dependency in the srcs list

* "srcs" list contains one main Rust source file,
  followed by optional dependent modules.
* A dependent module included in the "srcs" list is
  the module name prefixed with ":".
* Add a simple test.

Bug: 160331255
Test: make and manual test build dependencies on genrule modules
Change-Id: I4f079138c2599158810b6412fce81b612a3f64a4
diff --git a/rust/prebuilt.go b/rust/prebuilt.go
index 67d649d..3b4f40a 100644
--- a/rust/prebuilt.go
+++ b/rust/prebuilt.go
@@ -95,7 +95,8 @@
 func (prebuilt *prebuiltLibraryDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) android.Path {
 	prebuilt.exportLinkDirs(android.PathsForModuleSrc(ctx, prebuilt.Properties.Link_dirs).Strings()...)
 
-	srcPath := srcPathFromModuleSrcs(ctx, prebuilt.prebuiltSrcs())
+	srcPath, paths := srcPathFromModuleSrcs(ctx, prebuilt.prebuiltSrcs())
+	deps.SrcDeps = paths
 
 	prebuilt.unstrippedOutputFile = srcPath