rust: Add rustlibs auto dependency selection

Adds the rustlibs dependency type which will automatically select
between rlib and dylib based on the type of the library.

Bug: 143217452
Test: cd external/rust; mma
Change-Id: I97faadae98bf957090a32939cfb2d3a10f74a057

rust/proc_macro.go

@@ -76,3 +76,7 @@ func (procMacro *procMacroDecorator) getStem(ctx ModuleContext) string {
 
 	return stem + String(procMacro.baseCompiler.Properties.Suffix)
 }
+
+func (procMacro *procMacroDecorator) autoDep() autoDep {
+	return rlibAutoDep
+}