Move rpm stuff into a separate src/rpm/ directory

It is only of interest to rpm-based distros, we can move it out of src/core/
which is pretty busy.

meson.build

@@ -1746,6 +1746,7 @@ subdir('src/partition')
 subdir('src/portable')
 subdir('src/pstore')
 subdir('src/resolve')
+subdir('src/rpm')
 subdir('src/shutdown')
 subdir('src/sysext')
 subdir('src/systemctl')

src/core/meson.build

@@ -164,11 +164,9 @@ core_includes = [includes, include_directories('.')]
 
 systemd_sources = files('main.c')
 
-in_files = [['macros.systemd',   rpmmacrosdir],
-            ['system.conf',      pkgsysconfdir],
+in_files = [['system.conf',      pkgsysconfdir],
             ['user.conf',        pkgsysconfdir],
-            ['systemd.pc',       pkgconfigdatadir],
-            ['triggers.systemd', '']]
+            ['systemd.pc',       pkgconfigdatadir]]
 
 foreach item : in_files
         file = item[0]

src/rpm/meson.build

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+configure_file(
+        input : 'macros.systemd.in',
+        output : 'macros.systemd',
+        configuration : substs,
+        install_dir : rpmmacrosdir == 'no' ? '' : rpmmacrosdir)
+
+configure_file(
+        input : 'triggers.systemd.in',
+        output : 'triggers.systemd',
+        configuration : substs)
+# This doesn't get installed anywhere, it needs to included in the rpm spec
+# file definition.