feat: SDist CMake option

[henryiii]

Working on #392.

• Add to setuptools build_meta, too

For later PR:

+    libpl = sysconfig.get_config_var("LIBPL")
+    library = sysconfig.get_config_var("LIBRARY")
+
+    if libpl and library and Path(libpl).joinpath(library).is_file():
+        assert isinstance(libpl, str)
+        assert isinstance(library, str)
+        return Path(libpl) / library