add support for LOCAL_MODULE_STEM_32 and LOCAL_MODULE_STEM_64

Some executables will need to be built for both 32-bit and 64-bit.
For linker/linker64, debuggerd/debuggerd64, and a few more, they
will be installed in the same path (/system/bin), but with different
filenames.  Allow the module to specify LOCAL_MODULE_STEM_32 and
LOCAL_MODULE_STEM_64 to name the two versions.

Change-Id: I573e8678c7332245a064f31246be0a05f0a9e25f
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 5aa228f..8129014 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -199,6 +199,8 @@
 LOCAL_C_INCLUDES_64:=
 LOCAL_MODULE_PATH_32:=
 LOCAL_MODULE_PATH_64:=
+LOCAL_MODULE_STEM_32:=
+LOCAL_MODULE_STEM_64:=
 
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.