build: support LOCAL_*_32 and LOCAL_*_64

Support the following new variables based on whether the current multilib
target is 32 bit or 64 bit:
LOCAL_CFLAGS_32
LOCAL_CFLAGS_64
LOCAL_LDFLAGS_32
LOCAL_LDFLAGS_64
LOCAL_ASFLAGS_32
LOCAL_ASFLAGS_64
LOCAL_C_INCLUDES_32
LOCAL_C_INCLUDES_64

Change-Id: Ia868d56dff114be301bf8297eec768675f186927
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 8863fe6..32e1de6 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -162,6 +162,15 @@
 LOCAL_LDFLAGS_$(TARGET_2ND_ARCH):=
 endif
 
+LOCAL_CFLAGS_32:=
+LOCAL_CFLAGS_64:=
+LOCAL_LDFLAGS_32:=
+LOCAL_LDFLAGS_64:=
+LOCAL_ASFLAGS_32:=
+LOCAL_ASFLAGS_64:=
+LOCAL_C_INCLUDES_32:=
+LOCAL_C_INCLUDES_64:=
+
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.
 # Leave the current makefile to make sure we don't break anything