Don't expect that all files exist in strip-llvm.sh

If run multiple times, this removal would try to remove a file named
clang-*, which doesn't exist.

strip-llvm.sh

@@ -36,7 +36,7 @@ for i in bugpoint c-index-test clang-* diagtool dsymutil git-clang-format hmapto
         # was a plain number (as if the original name was clang-7); if it wasn't
         # empty, remove the tool.
         if [ "$(echo $suffix | tr -d '[0-9]')" != "" ]; then
-            rm $i
+            rm -f $i
         fi
         ;;
     llvm-ar|llvm-cvtres|llvm-dlltool|llvm-nm|llvm-objdump|llvm-ranlib|llvm-rc|llvm-readobj|llvm-strings|llvm-pdbutil)