configure: use shared-glapi when more than one gl* API is used

configure: use shared-glapi when more than one gl* API is used

Current behaviour states that shared-glapi is usefull when building
with dri, which is not the case. Shared-glapi is used to dispatch
the gl* functions across the one or more gl api's which can be dri
based but do not need to be.

Fixed the following build

 ./configure --enable-gles2 --disable-dri --enable-gallium-egl \
      --with-egl-platforms=fbdev --with-gallium-drivers=swrast

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75098
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>