attn@timhoffm: breaking#11235 into smaller pieces.

• Reformat a bunch of strings.
• Rely on Python's tarfile module to extract the FreeType tarball,
  instead of the "tar" executable (because we need to use Python's
  tarfile on Windows anyways, so we may as well do it on all OSes).
• For the Unix build, call./configure andmake without
  shell=True, instead setting CFLAGS in the environment as needed.

PR Summary

PR Checklist

• Has Pytest style unit tests
• Code is PEP 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way