Skip default dependencies for header libraries

Header libraries don't compile anything, so they don't need the
default stl and libclang_rt dependencies.  Trimming the dependencies
simplifies using header libraries for LLNDK libraries, which need
extra variants that don't exist for the default dependencies.

Test: m checkbuild
Change-Id: Ib9864c3cc7048b2cc52acf304830777b65a51877

cc/linker.go

@@ -322,7 +322,7 @@ func (linker *baseLinker) linkerDeps(ctx DepsContext, deps Deps) Deps {
 
 	if ctx.toolchain().Bionic() {
 		// libclang_rt.builtins has to be last on the command line
-		if !Bool(linker.Properties.No_libcrt) {
+		if !Bool(linker.Properties.No_libcrt) && !ctx.header() {
 			deps.LateStaticLibs = append(deps.LateStaticLibs, config.BuiltinsRuntimeLibrary(ctx.toolchain()))
 		}
 

cc/stl.go

@@ -62,6 +62,8 @@ func (stl *stl) begin(ctx BaseModuleContext) {
 		s := ""
 		if stl.Properties.Stl != nil {
 			s = *stl.Properties.Stl
+		} else if ctx.header() {
+			s = "none"
 		}
 		if ctx.useSdk() && ctx.Device() {
 			switch s {