buildgcc: Check exit status of `getopt`

We accidentally checked the status of `eval` instead.

Change-Id: I1ba258944184ed707ed1f176e528d8266656cb59
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/16680
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
1 file changed