Gawk cause linuxboot boards to fail building

[tlaurion]

@NHellFire #811 merge causes linuxboot based board to fail building:

user@localhost:~/heads$ make BOARD=qemu-linuxboot 
2020-09-25 15:45:47-04:00 Wrong gawk detected: 4.2.1
/home/user/heads/boards/qemu-linuxboot/qemu-linuxboot.config:49: warning: overriding recipe for target 'run'
Makefile:54: warning: ignoring old recipe for target 'run'
Makefile:198: warning: overriding recipe for target 'all'
Makefile:54: warning: ignoring old recipe for target 'all'
modules/coreboot:13: *** recipe commences before first target.  Stop.

(Wasn't cathced since no linuxboot based boards are in CIs.)

[tlaurion]

Not linked and spoke too fast. Its link to those boards not having coreboot versions specified....