graphics/colmap: unbreak OPENMP with GCC 9

In file included from lib/VLFeat/kmeans.h:21,

from lib/VLFeat/kmeans.c:363:

lib/VLFeat/kmeans.c: In function '_vl_kmeans_quantize_f':
lib/VLFeat/mathop.h:92:37: error: 'vl_infinity_d' not specified in enclosing 'parallel'

92 | #define VL_INFINITY_D (vl_infinity_d.value)
   |                       ~~~~~~~~~~~~~~^~~~~~~

lib/VLFeat/kmeans.c:685:34: note: in expansion of macro 'VL_INFINITY_D'

685 |       TYPE bestDistance = (TYPE) VL_INFINITY_D ;
    |                                  ^~~~~~~~~~~~~

In file included from lib/VLFeat/kmeans.c:1782:
lib/VLFeat/kmeans.c:672:9: error: enclosing 'parallel'

672 | #pragma omp parallel default(none) \
    |         ^~~

In file included from lib/VLFeat/kmeans.c:1788:
lib/VLFeat/kmeans.c: In function '_vl_kmeans_quantize_d':
lib/VLFeat/kmeans.c:685:27: error: 'vl_infinity_d' not specified in enclosing 'parallel'

685 |       TYPE bestDistance = (TYPE) VL_INFINITY_D ;

lib/VLFeat/kmeans.c:672:9: error: enclosing 'parallel'

672 | #pragma omp parallel default(none) \
    |         ^~~

PR: 238330
Reported by: antoine (via exp-run)