[RenderScript] Update the build rules for x86_64 support lib.

Bug: 19735423

  - Unlike other archs, x86_64 has both usr/lib and usr/lib64. we need
    to search for libm.so and libc.so in lib64/. Otherwise the linker
    will report error.

Change-Id: I2859bee066a9eb100828d90da8adf0f9817d77e6
diff --git a/core/config.mk b/core/config.mk
index d25b323..b7e518f 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -861,7 +861,8 @@
 RS_PREBUILT_CLCORE := prebuilts/sdk/renderscript/lib/$(TARGET_ARCH)/librsrt_$(TARGET_ARCH).bc
 RS_PREBUILT_COMPILER_RT := prebuilts/sdk/renderscript/lib/$(TARGET_ARCH)/libcompiler_rt.a
 ifeq (true,$(TARGET_IS_64_BIT))
-RS_PREBUILT_LIBPATH := -L prebuilts/ndk/current/platforms/android-21/arch-$(TARGET_ARCH)/usr/lib
+RS_PREBUILT_LIBPATH := -L prebuilts/ndk/current/platforms/android-21/arch-$(TARGET_ARCH)/usr/lib64 \
+                       -L prebuilts/ndk/current/platforms/android-21/arch-$(TARGET_ARCH)/usr/lib
 else
 RS_PREBUILT_LIBPATH := -L prebuilts/ndk/current/platforms/android-9/arch-$(TARGET_ARCH)/usr/lib
 endif