buildgcc: Re-add some break statements

While some of the case .. break statement actually weren't needed,
too are, since otherwise the option parsing loop hangs.

Exit conditions for that endless loop: "--" or no more arguments,
in line with GNU command line parsing rules.

Change-Id: I0dbc35e530fb8c93a0f7de05ac47f325555ad4a4
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/3418
Tested-by: build bot (Jenkins)
Reviewed-by: David Hubbard <david.c.hubbard+coreboot@gmail.com>

util/crossgcc/buildgcc

@@ -215,9 +215,9 @@ while true ; do
 		-G|--gdb)	shift; SKIPGDB=0;;
 		-S|--scripting) shift; SKIPPYTHON=0;;
 		-y|--ccache)	shift; USECCACHE=1;;
-		--)		shift;;
+		--)		shift; break;;
 		-*)		printf "Invalid option\n\n"; myhelp; exit 1;;
-		*)		;;
+		*)		break;;
 	esac
 done