Handle Flutter SDK paths with spaces in doctor (#6578)
diff --git a/bin/internal/update_dart_sdk.sh b/bin/internal/update_dart_sdk.sh
index 58c63e1..76177c5 100755
--- a/bin/internal/update_dart_sdk.sh
+++ b/bin/internal/update_dart_sdk.sh
@@ -5,7 +5,7 @@
set -e
-FLUTTER_ROOT=$(dirname $(dirname $(dirname "${BASH_SOURCE[0]}")))
+FLUTTER_ROOT="$(dirname "$(dirname "$(dirname "${BASH_SOURCE[0]}")")")"
DART_SDK_PATH="$FLUTTER_ROOT/bin/cache/dart-sdk"
DART_SDK_STAMP_PATH="$FLUTTER_ROOT/bin/cache/dart-sdk.stamp"