dlsym: Fix build under uClibc
dlsym: Fix build under uClibc

uClibc defines the __GLIBC__ macro too (I know, right?), so verify that
__UCLIBC__ is not defined before we can use glibc-specific internal
functions.

Signed-off-by: Paul Cercueil <a027184a55211cd23e3f3094f1fdc728df5e0500@crapouillou.net>

apitrace/apitrace,apitrace/apitrace,apitrace/apitrace,apitrace/apitrace