Build fails to pass -std=c99 flag: blosc2.h: error: ‘for’ loop initial declaration used outside C99 mode

[barracuda156]

blosc2 itself sets -std=gnu99 in its own CMakeLists, however those are not used by py-blosc2 when external blosc2 is linked against. So the flag is not passed, but it is required:

In file included from /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_python_py-blosc2/py311-blosc2/work/blosc2-2.5.1/_skbuild/macosx-10.6-ppc-3.11/cmake-build/blosc2/blosc2_ext.c:1253:
/opt/local/include/blosc2.h: In function ‘blosc2_meta_exists’:
/opt/local/include/blosc2.h:2162: error: ‘for’ loop initial declaration used outside C99 mode

[FrancescAlted]

Hi, Can you provide a PR for this? Thanks!