Consider `pkg-config` for finding the compiler flags?

[dipterix]

This issue is a continuation of https://github.com/hhoeflin/hdf5r/issues/165

Background:

Recently homebrew has changed their HDF5 from using autoconf to cmake. The result is h5cc -show (used by configure.ac) is broken, causing hdf5r to crash during compiling.

Besides, HDF5Groups have a discussion of kicking autotools out and embrace cmake (https://www.hdfgroup.org/2022/11/can-we-remove-the-autotools/) in its new versions.

Currently if you are using Mac and install the newest HDF5, it's most likely that the HDF5 is configured with cmake and pkg-config is installed (brew list it as the dependence). In fact, Python package h5py uses pkgconfig to determine the flags too.

Maybe it's time to consider adding pkg-config as a back-up method in case h5cc -show results in error?