Correct condition style for determining musl ldd

Author: tesuji

rustup-init.sh

@@ -172,7 +172,7 @@ get_architecture() {
         if [ "$(uname -o)" = Android ]; then
             _ostype=Android
         fi
-        if [ "$(ldd --version 2>&1 | grep 'musl')" ]; then
+        if ldd --version 2>&1 | grep -q 'musl'; then
             _clibtype="musl"
         fi
     fi