Turning on GNU make checker

[Ikumi Keita]

Hi all,

Current build framework of AUCTeX requires GNU make, so it would be
reasonable to check whether "make" command is GNU make or not, and, if
not, try to find GNU make under other name such as "gmake".

Fortunately, there is already such infrastructure in the source of emacs
28.1, which I copied into my local AUCTeX source tree as the attached
patch. What do you think about the idea to include it in the next
release?

(But I don't know the exact minimum version of required GNU make, so
3.81 might be wrong for AUCTeX. Does anyone know the detail? Or should
we just leave the minimum version unspecified?)

Regards,
Ikumi Keita
#StandWithUkraine #StopWarInUkraine

0001-Adapt-for-system-where-GNU-make-is-gmake.patch
Description: tentative patch