Building Notmuch on macOS is known to cause problems because the Notmuch
distribution archive contains two files named "version". These clash
with the <version> keyword as defined in C++20 [1] and will likely
become obvious on other platforms as well once Compilers adopt the new
standard.

The two affected files in the Notmuch Git tree are

  /bindings/python-cffi/version
  /version

I suggest to rename them both to version.txt. The attached patch can
then be applied to make the necessary build file changes.

-Ralph

[1] https://en.cppreference.com/w/cpp/20#New_headers