package/gettext-tiny: fix build of libintl.a

package/gettext-tiny: fix build of libintl.a

Since libintl.a can be pulled in during the build of other shared libs,
it must be compiled with -fPIC, which is what gettext-tiny's Makefile
would do.

Since we provide our own CFLAGS, they override those in the Makefile.

Fix that by ensuring that -fPIC is used when building the static
library.

Fixes:
    http://autobuild.buildroot.org/results/a38/a3800fd4ef2536cc2b82d38ea752baa2b227bc64/

Also, since GETTEXT_TINY_OPTS is used only once and contains a single
definition, get rid of it altogether.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Vadim Kochan <vadim4j@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>