Ensure that these scripts are executed by the standard 'sh', rather
than whatever your current shell happens to be.

If pkg-config is installed, then libsndfile's configure will try to
use pkg-config to check whether the optional dependencies (flac, ogg,
vorbis, opus, mpg123) are present.  (It will conclude that the
packages are present because the appropriate *_CFLAGS and *_LIBS are
set.)

If pkg-config isn't installed, then --enable-external-libs and
--enable-mpeg must be set explicitly in order to use these packages.

Remove the old workflow using CentOS 7 (which is unsupported and
broken) and replace it with one using a newer (glibc 2.28 based)
container from pypa.

Note that GitHub's "macos-13" runners are x86-64 whereas "macos-14"
runners are arm64.

The libvorbis configure script will try multiple methods to find the
libogg headers and library.  Using the pkg-config variables is the
newer and probably-more-stable method.

Instead of using an arm64 native compiler and everything else running
inside an emulator, use the aarch64-linux-gnu cross compiler provided
by Debian 10 (glibc 2.28).

In libsndfile 1.2.1 and 1.2.2, the spelling of "mpg123" in the cmake
variable names was changed to lowercase.