gpac-libgpac port not building on amd64

[Troy]

I just did a successful portupgrade of multimedia/gpac-libgpac but when
trying to upgrade the exact same port on amd64, it fails with the
following error.

Thanks

cc -O3  -O2 -fno-strict-aliasing -pipe  -fPIC -pthread
-fno-strict-aliasing -Wno-pointer-sign
-I/usr/ports/multimedia/gpac-libgpac/work/gpac/include  -I../
-DGPAC_HAVE_CONFIG_H  -fPIC -DPIC -c compositor/events.c -o
compositor/events.opic
compositor/events.c: In function 'load_text_node':
compositor/events.c:239: warning: passing argument 3 of 'gf_utf8_wcstombs'
from incompatible pointer type
compositor/events.c:247: warning: passing argument 3 of 'gf_utf8_wcstombs'
from incompatible pointer type
cc -O3  -O2 -fno-strict-aliasing -pipe  -fPIC -pthread
-fno-strict-aliasing -Wno-pointer-sign
-I/usr/ports/multimedia/gpac-libgpac/work/gpac/include  -I../
-DGPAC_HAVE_CONFIG_H  -fPIC -DPIC -c compositor/font_engine.c -o
compositor/font_engine.opic
cc -O3  -O2 -fno-strict-aliasing -pipe  -fPIC -pthread
-fno-strict-aliasing -Wno-pointer-sign
-I/usr/ports/multimedia/gpac-libgpac/work/gpac/include  -I../
-DGPAC_HAVE_CONFIG_H  -fPIC -DPIC -c compositor/hardcoded_protos.c -o
compositor/hardcoded_protos.opic
cc -O3  -O2 -fno-strict-aliasing -pipe  -fPIC -pthread
-fno-strict-aliasing -Wno-pointer-sign
-I/usr/ports/multimedia/gpac-libgpac/work/gpac/include  -I../
-DGPAC_HAVE_CONFIG_H  -fPIC -DPIC -c compositor/mesh.c -o
compositor/mesh.opic
In file included from compositor/mesh.c:33:
compositor/gl_inc.h:45:19: error: GL/gl.h: No such file or directory
gmake: *** [compositor/mesh.opic] Error 1
*** Error code 2

Stop in /usr/ports/multimedia/gpac-libgpac.