setup.py: drop path prefix from man install

If the directory is a relative path, it is interpreted relative to the
installation prefix (Python’s sys.prefix for pure-Python packages,
sys.exec_prefix for packages that contain extension modules).
So the sys.prefix should not be joined because the correct one will be
added regardless. The reason why a relative path is going to work is
because the installation path is built internally joining python root
with python prefix, thus forming the correct path $(TARGET_DIR)/usr.
(https://docs.python.org/3/distutils/setupscript.html#installing-additional-files)

For this man file install scenario, joining the sys.prefix makes the
path absolute (this was previously working by accident).

Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>

setup.py

@@ -136,7 +136,7 @@ setup(name='setools',
       cmdclass={'build_qhc': QtHelpCommand, 'clean': CleanCommand},
       packages=['setools', 'setools.diff', 'setoolsgui', 'setoolsgui.apol'],
       scripts=['apol', 'sediff', 'seinfo', 'seinfoflow', 'sesearch', 'sedta'],
-      data_files=[(join(sys.prefix, 'share/man/man1'), glob.glob("man/*.1"))],
+      data_files=[('share/man/man1', glob.glob("man/*.1"))],
       package_data={'': ['*.ui', '*.qhc', '*.qch'], 'setools': ['perm_map']},
       ext_modules=cythonize(ext_py_mods, include_path=['setools/policyrep'],
                             annotate=cython_annotate,