Add -c flag to git ls-files.

bin/compile

@@ -66,10 +66,13 @@ chmod +x boot.sh
 # but since the PHP buildpack moves everything out of $BUILD_DIR into
 # www/ we can't rely on that implementation and need to duplicate it here.
 
-if [ "$(cd $BUILD_DIR/www && git ls-files -o -i --exclude-from=.slugignore 2> /dev/null)" != "" ]; then
-    echo "-----> Deleting files matching .slugignore patterns."
+if [ -r $BUILD_DIR/www/.slugignore ]; then
+    unset GIT_DIR
     cd www
-    git ls-files -z -o -i --exclude-from=.slugignore | xargs -0 rm
+    if [ "$(git ls-files -c -o -i --exclude-from=.slugignore)" != "" ]; then
+        echo "-----> Deleting files matching .slugignore patterns."
+        git ls-files -z -c -o -i --exclude-from=.slugignore | xargs -0 rm
+    fi
     cd ..
 fi