buildgcc: Fix GNU getopt usage

Looks like this never worked correctly: There are three argument formats
to GNU getopt and none of them matches what we fed it. The missing
double dash before the `set` arguments proves that we always called it
with parameters that `getopt` did NOT parse.

Change-Id: Ib8343976ef31774b18567a9fc9745a9f58dd287a
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/16679
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)
1 file changed