Makefile: Add a DISABLE_CLOCK_GETTIME option

Allows to force-disable the use of clock_gettime() at build time,
falling back to busy-looping for udelay. This is useful when building
for systems which are known to lie about the resolution of
clock_gettime(), such as Linux guests running under the Muen Separation
Kernel.

Change-Id: I645a5d3f29ffdbd24a58127ab73d7d8755304f45
Signed-off-by: Martin Lucina <martin@lucina.net>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/48796
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
1 file changed