Accept compiler and flags from environment

[plusky]

When packaging for distribution (such as openSUSE), distributions we want to specify CFLAGS/LDFLAGS and in some cases compiler as well.

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[NotTsunami]

Typo :)

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[CounterPillow]

Did you see #92?

[plusky]

Did you see #92?

Yes I did see it, it does not allow specifying compiler, and instead of := there is some funky "override CFLAGS" used. Last but not leas, current makefile does not handle LDFLAGS correctly, which is also fixed here.

[scop]

Seems this was at least partially taken care of in 4a35d30