Define and use %{_py3_shebang_s} in the shebang macros for easier opt-out

This is in-line with https://fedoraproject.org/wiki/Changes/PythonSafePath#Opting_out

Backported from https://src.fedoraproject.org/rpms/python-rpm-macros/pull-request/141

macros.python

@@ -12,7 +12,8 @@
 %python_cache_tag %(RPM_BUILD_ROOT= %{__python} -Esc "import sys; print(sys.implementation.cache_tag)")
 
 %py_setup setup.py
-%py_shbang_opts -s
+%_py_shebang_s s
+%py_shbang_opts -%{?_py_shebang_s}
 %py_shbang_opts_nodash %(opts=%{py_shbang_opts}; echo ${opts#-})
 %py_shebang_flags %(opts=%{py_shbang_opts}; echo ${opts#-})
 %py_shebang_fix %{expand:\\\

macros.python3

@@ -10,7 +10,8 @@
 %python3_cache_tag %(RPM_BUILD_ROOT= %{__python3} -Ic "import sys; print(sys.implementation.cache_tag)")
 %py3dir %{_builddir}/python3-%{name}-%{version}-%{release}
 
-%py3_shbang_opts -s
+%_py3_shebang_s s
+%py3_shbang_opts -%{?_py3_shebang_s}
 %py3_shbang_opts_nodash %(opts=%{py3_shbang_opts}; echo ${opts#-})
 %py3_shebang_flags %(opts=%{py3_shbang_opts}; echo ${opts#-})
 %py3_shebang_fix %{expand:\\\

python-rpm-macros.spec

@@ -148,6 +148,7 @@ install -m 755 brp-* %{buildroot}%{_rpmconfigdir}/redhat/
 %changelog
 * Tue Jul 19 2022 Miro Hrončok <mhroncok@redhat.com> - 3.10-12
 - Define %%python3_cache_tag / %%python_cache_tag, e.g. cpython-311
+- Define and use %%{_py3_shebang_s} in the shebang macros for easier opt-out
 
 * Mon Feb 07 2022 Miro Hrončok <mhroncok@redhat.com> - 3.10-11
 - Set $RPM_BUILD_ROOT in %%{python3_...} macros

tests/test_evals.py

@@ -334,6 +334,13 @@ def test_py3_shebang_fix_custom_shebang_flags():
     assert shell_stdout('\n'.join(lines)) == '-kaEs'
 
 
+@pytest.mark.parametrize('_py3_shebang_s', [None, '%{nil}'])
+def test_py3_shebang_fix_undefined_py3_shebang_s(_py3_shebang_s):
+    lines = rpm_eval('%py3_shebang_fix arg1 arg2', _py3_shebang_s=_py3_shebang_s)
+    lines[-1] = 'echo $shebang_flags'
+    assert shell_stdout('\n'.join(lines)) == '-k'
+
+
 @pytest.mark.parametrize('flags', [None, '%{nil}'])
 def test_py3_shebang_fix_no_shebang_flags(flags):
     lines = rpm_eval('%py3_shebang_fix arg1 arg2', py3_shebang_flags=flags)