fix(gcc): quote the command name $1 for custom IFS

Author: akinomyoga

completions/gcc

@@ -7,7 +7,7 @@ _comp_cmd_gcc()
 
     # Test that GCC is recent enough and if not fallback to
     # parsing of --completion option.
-    if ! $1 --completion=" " 2>/dev/null; then
+    if ! "$1" --completion=" " 2>/dev/null; then
         if [[ $cur == -* ]]; then
             local cc=$("$1" -print-prog-name=cc1 2>/dev/null)
             [[ $cc ]] || return