Allow execution of shell-scripted systemd generators

While systemd recommends to use native binaries as generators due to
performance reasons, there is nothing that really prevents from them
being shell scripts.

This is Gentoo-specific as the affected generator is provided by
the distribution, not by upstream systemd.

Signed-off-by: Krzysztof Nowicki <krissn@op.pl>

policy/modules/system/systemd.te

@@ -443,6 +443,10 @@ systemd_log_parse_environment(systemd_generator_t)
 
 term_use_unallocated_ttys(systemd_generator_t)
 
+ifdef(`distro_gentoo',`
+	corecmd_shell_entry_type(systemd_generator_t)
+')
+
 optional_policy(`
 	fstools_exec(systemd_generator_t)
 ')