build: Do not include os2compat.[ch]
kLIBC does not need os2compat.[ch]
* gettext-runtime/configure.ac (AH_BOTTOM): Do not include
intl/os2compat.h on kLIBC.
* gettext-runtime/intl/osdep.c: Do not include os2compat.c on kLIBC.
* gettext-tools/configure.ac (AH_BOTTOM): Do not include
intl/os2compat.h on kLIBC.
Copyright-paperwork-exempt: yes
