Initialize data directories with --lc-messages=C for tests.

Commit db6d9891e8 changed them to be initialized with --no-locale, but
that reduced the test coverage for non-C locales.

Discussion: https://postgr.es/m/0d47e5ecc037b3908149aad5f2a987793cf938bd.camel%40j-davis.com

meson.build

@@ -3115,7 +3115,7 @@ sys.exit(sp.returncode)
 ''',
        test_initdb_template,
        temp_install_bindir / 'initdb',
-       '--auth', 'trust', '--no-sync', '--no-instructions', '--no-locale',
+       '--auth', 'trust', '--no-sync', '--no-instructions', '--lc-messages=C',
        '--no-clean'
      ],
      priority: setup_tests_priority - 1,

src/Makefile.global.in

@@ -423,7 +423,7 @@ ifeq ($(MAKELEVEL),0)
 	$(MAKE) -C '$(top_builddir)' DESTDIR='$(abs_top_builddir)'/tmp_install install >'$(abs_top_builddir)'/tmp_install/log/install.log 2>&1
 	$(MAKE) -j1 $(if $(CHECKPREP_TOP),-C $(CHECKPREP_TOP),) checkprep >>'$(abs_top_builddir)'/tmp_install/log/install.log 2>&1
 
-	$(with_temp_install) initdb --auth trust --no-sync --no-instructions --no-locale --no-clean '$(abs_top_builddir)'/tmp_install/initdb-template >>'$(abs_top_builddir)'/tmp_install/log/initdb-template.log 2>&1
+	$(with_temp_install) initdb --auth trust --no-sync --no-instructions --lc-messages=C --no-clean '$(abs_top_builddir)'/tmp_install/initdb-template >>'$(abs_top_builddir)'/tmp_install/log/initdb-template.log 2>&1
 endif
 endif
 endif