package/glmark2: drm-glesv2 needs libgbm

Fixes build error with defconfig from:
http://autobuild.buildroot.net/results/e393dbfba7c2989fe983df47ea0638c3ba62ae7a/

  Checking for 'libdrm': yes
  Checking for 'gbm'   : not found

after http://patchwork.ozlabs.org/project/buildroot/patch/20200104193919.91589-1-bernd.kuhls@t-online.de/
was applied. Both patches are needed to fix the build error.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/glmark2/Config.in

@@ -5,6 +5,7 @@ config BR2_PACKAGE_GLMARK2_FLAVOR_DRM_GLESV2
 	bool
 	default y
 	depends on BR2_PACKAGE_HAS_LIBEGL
+	depends on BR2_PACKAGE_HAS_LIBGBM
 	depends on BR2_PACKAGE_HAS_LIBGLES
 	depends on BR2_PACKAGE_HAS_UDEV
 	depends on BR2_TOOLCHAIN_HAS_THREADS  # libpthread-stubs -> libdrm

package/glmark2/glmark2.mk

@@ -11,7 +11,7 @@ GLMARK2_LICENSE_FILES = COPYING COPYING.SGI
 GLMARK2_DEPENDENCIES = host-pkgconf jpeg libegl libpng
 
 ifeq ($(BR2_PACKAGE_GLMARK2_FLAVOR_DRM_GLESV2),y)
-GLMARK2_DEPENDENCIES += libdrm libgles udev
+GLMARK2_DEPENDENCIES += libdrm libgbm libgles udev
 GLMARK2_FLAVORS += drm-glesv2
 endif