M_PI is not part of C99 or C++ and thus aren't provided in all configurations.
This used to be handled in reference_math.c directly but was recently removed.
Just tweak the M_PI handling in the compatibility headers to restore builds.
The maintenance of the conformance tests is moving to Github.
This commit contains all the changes that have been done in
Gitlab since the first public release of the conformance tests.
Signed-off-by: Kevin Petit <kevin.petit@arm.com>
