build: Fix link error on MSVC with --disable-shared.
* gettext-tools/tests/setlocale.c (setlocale): Define to fake_setlocale on
native Windows.
* gettext-tools/tests/format-c-3-prg.c (setlocale): Likewise.
* gettext-tools/tests/format-c-4-prg.c (setlocale): Likewise.
* gettext-tools/tests/plural-1-prg.c (setlocale): Likewise.
* gettext-tools/tests/tstgettext.c (setlocale): Likewise.
* gettext-tools/tests/tstngettext.c (setlocale): Likewise.
