Check that the LLVM source directory exists before changing to it.

build_opts.sh

@@ -2,6 +2,7 @@
 LLVM_PATH=`llvm-config --src-root`
 LIBOBJC_PATH=`pwd`
 if [ x$LLVM_PATH != x ] ; then
+	if [ -d $LLVM_PATH ] ; then
 		cd $LLVM_PATH
 		cd lib/Transforms
 		if [ ! -d GNURuntime ] ; then
@@ -16,3 +17,4 @@ if [ x$LLVM_PATH != x ] ; then
 		$1 $2
 		cd ..
 	fi
+fi