Add %python3_platform useful for PYTHONPATH on arched builds

This is mostly used when building Sphinx docs on arched build.

Previously:

  PLATFORM=$(python3 -c "import sysconfig; print(sysconfig.get_platform())")
  export PYTHONPATH=../build/lib.${PLATFORM}-%{python3_version}
  make man

Or:

  PYTHONPATH=`realpath ../build/lib.linux*` make

Or:

  PYTHONPATH=$(echo $PWD/build/lib.linux-*) make html

Now:

  PYTHONPATH=../build/lib.%{python3_platform}-%{python3_version}

macros.python3

@@ -3,6 +3,7 @@
 %python3_sitearch %(%{__python3} -Ic "from distutils.sysconfig import get_python_lib; print(get_python_lib(1))")
 %python3_version %(%{__python3} -Ic "import sys; sys.stdout.write(sys.version[:3])")
 %python3_version_nodots %(%{__python3} -Ic "import sys; sys.stdout.write(sys.version[:3].replace('.',''))")
+%python3_platform %(%{__python3} -Ic "import sysconfig; print(sysconfig.get_platform())")
 %py3dir %{_builddir}/python3-%{name}-%{version}-%{release}
 
 %py3_shbang_opts -s

python-rpm-macros.spec

@@ -1,6 +1,6 @@
 Name:           python-rpm-macros
 Version:        3
-Release:        30%{?dist}
+Release:        31%{?dist}
 Summary:        The unversioned Python RPM macros
 
 License:        MIT
@@ -71,6 +71,9 @@ install -m 644 %{SOURCE0} %{SOURCE1} %{SOURCE2} %{SOURCE3} %{SOURCE4} \
 
 
 %changelog
+* Tue Jul 03 2018 Miro Hrončok <mhroncok@redhat.com> - 3-31
+- Add %%python3_platform useful for PYTHONPATH on arched builds
+
 * Mon Jun 18 2018 Jason L Tibbitts III <tibbs@math.uh.edu> - 3-30
 - Add %%pypi_source macro, as well as %%__pypi_url and
   %%_pypi_default_extension.