Support libboost_<module>-mt-<arch>.a for mingw-w64

Alas b2’s tagged layout now (I believe since boost 1.69, but not entirely sure) also includes the Windows-style x86 / x64 tags in their library naming when building for mingw-w64.

This means that dependencies/boost.py’s

# Note that we should also try to support:
# mingw-w64 / Windows : libboost_<module>-mt.a            (location = <prefix>/mingw64/lib/)
#                       libboost_<module>-mt.dll.a

is now insufficient, we have to check for libboost_<module>-mt-<arch>.a and libboost_<module>-mt-<arch>.dll.a.

I guess always checking both would be the most robust?

[mensinda]

Really, only boost can get away with this ridiculus tag layout without any working dependency system…

@jpakkane This issue should not block the -rc[0-9]+ releases, but should be resolved before the final 0.56.0 release since I would classify this as a bug fix.

[fiesh]

Ok, I’m sorry, that was my stupidity. It turns out I screwed up the meson update and was actually using an older version – and then was misled by the comments indicating an older check than what was actually done. Now updating meson properly resolves the issue.

I’m sorry about this!