meson: allow building resolved and machined without nss modules

This adds -Dnss-resolve= and -Dnss-mymachines= meson options.
By using this option, e.g., resolved can be built without nss-resolve.
When no nss modules are built, then test-nss is neither built.

Also, This changes the option name -Dmyhostname= to -Dnss-myhostname=
for consistency to other nss related options.

Closes #9596.

src/test/meson.build

@@ -645,7 +645,7 @@ tests += [
         [['src/test/test-nss.c'],
          [],
          [libdl],
-         '', 'manual'],
+         'ENABLE_NSS', 'manual'],
 
         [['src/test/test-umount.c',
           'src/core/mount-setup.c',

src/test/test-nss.c

@@ -431,13 +431,13 @@ static int parse_argv(int argc, char **argv,
                 modules = strv_new(argv[1], NULL);
         else
                 modules = strv_new(
-#if ENABLE_MYHOSTNAME
+#if ENABLE_NSS_MYHOSTNAME
                                 "myhostname",
 #endif
-#if ENABLE_RESOLVE
+#if ENABLE_NSS_RESOLVE
                                 "resolve",
 #endif
-#if ENABLE_MACHINED
+#if ENABLE_NSS_MYMACHINES
                                 "mymachines",
 #endif
                                 "dns",