Update frameworks/rs/ for LLVM rebase to r256229

http://b/26987366

Change-Id: I7448ec907a781f86d0db48507ad2751e0ed9f36c
diff --git a/update_rs_prebuilts.sh b/update_rs_prebuilts.sh
index 62e4d19..d9486ff 100755
--- a/update_rs_prebuilts.sh
+++ b/update_rs_prebuilts.sh
@@ -34,6 +34,9 @@
 export ANDROID_USE_BUILDCACHE=false
 export FORCE_BUILD_LLVM_COMPONENTS=true
 
+# Skip building LLVM and compiler-rt tests while updating prebuilts
+export SKIP_LLVM_TESTS=true
+
 # Ensure that we have constructed the latest "bcc" for the host. Without
 # this variable, we don't build the .so files, hence we never construct the
 # actual required compiler pieces.