Merge "Fix run-buildtools-binary.sh to work on my computer"
diff --git a/tools/run-buildtools-binary.sh b/tools/run-buildtools-binary.sh
index 4a9cd47..93eadb0 100644
--- a/tools/run-buildtools-binary.sh
+++ b/tools/run-buildtools-binary.sh
@@ -21,7 +21,7 @@
 
 readonly PROJECT_ROOT="$(cd -P ${BASH_SOURCE[0]%/*}/..; pwd)"
 
-case "$(uname -s | tr [:upper:] [:lower:])" in
+case "$(uname -s | tr '[A-Z]' '[a-z]')" in
   darwin)
     readonly OS="mac";;
   linux)