Remove extra LOCAL_CXX_STL := none

This was always being set in cc.Module.AndroidMk(), so we don't need to
declare it again. This was causing problems for cc_binary modules that
were using the NDK, since LOCAL_NDK_STL_VARIANT must be used instead.

Test: Manually put ifneq ($(LOCAL_CXX_STL),none); $(error) checks
Change-Id: If937b7b5ad30936e08c99f62ccf83b78d196dbfe
diff --git a/cc/androidmk.go b/cc/androidmk.go
index 831c0fb..285a5a7 100644
--- a/cc/androidmk.go
+++ b/cc/androidmk.go
@@ -129,7 +129,6 @@
 
 	ret.Class = "EXECUTABLES"
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) error {
-		fmt.Fprintln(w, "LOCAL_CXX_STL := none")
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 		if Bool(binary.Properties.Static_executable) {
 			fmt.Fprintln(w, "LOCAL_FORCE_STATIC_EXECUTABLE := true")
@@ -157,7 +156,6 @@
 	ret.Class = "STATIC_LIBRARIES"
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) error {
 		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+outputFile.Ext())
-		fmt.Fprintln(w, "LOCAL_CXX_STL := none")
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 
 		return nil