correct usage instruction of make.sh
diff --git a/make.sh b/make.sh
index 140e935..e66b96c 100755
--- a/make.sh
+++ b/make.sh
@@ -53,5 +53,5 @@
   "cygwin-mingw64" ) CROSS=x86_64-w64-mingw32- build;;
   "clang" ) CC=clang build;;
   "gcc" ) CC=gcc build;;
-  * ) echo "Usage: make [nix32|cross-win32|cross-win64|cygwin-mingw32|cygwin-mingw64|clang|gcc]"; exit 1;;
+  * ) echo "Usage: make.sh [nix32|cross-win32|cross-win64|cygwin-mingw32|cygwin-mingw64|clang|gcc]"; exit 1;;
 esac