systemd: Skip parsing on musl based targets

systemd on musl doesn't yet work even though we have patches to make it
compile it fails to run, therefore lets skip building it for now

(From OE-Core rev: a1986acf66381dee18f5c8deae7cf52490d0f58a)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/systemd/systemd_228.bb

@@ -443,4 +443,8 @@ pkg_prerm_udev-hwdb () {
 python () {
     if not bb.utils.contains ('DISTRO_FEATURES', 'systemd', True, False, d):
         raise bb.parse.SkipPackage("'systemd' not in DISTRO_FEATURES")
+
+    import re
+    if re.match('.*musl*', d.getVar('TARGET_OS', True)) != None:
+        raise bb.parse.SkipPackage("Not _yet_ supported on musl based targets")
 }