Switch to use slang/rs_version.mk for consistency.

Change-Id: Ibfda53448570be58941133cb53c1bbb90391aa30
diff --git a/driver/runtime/build_bc_lib_internal.mk b/driver/runtime/build_bc_lib_internal.mk
index b27e163..478ab30 100644
--- a/driver/runtime/build_bc_lib_internal.mk
+++ b/driver/runtime/build_bc_lib_internal.mk
@@ -36,7 +36,7 @@
 bc_translated_clang_cc1_cflags := $(addprefix -Xclang , $(bc_clang_cc1_cflags))
 
 bc_cflags := -MD \
-             -DRS_VERSION=$(RS_VERSION) \
+             $(RS_VERSION_DEFINE) \
              -std=c99 \
              -c \
              -O3 \