gl: fix build with more recent versions of MinGW

6 jobs for fix-mingw6 in 25 minutes and 5 seconds (queued for 1 second)
Status Job ID Name Coverage
  Preparation
passed #74667
gst indent

00:00:29

passed #74666
manifest

00:00:18

 
  Build
passed #74668
build fedora x86_64

00:02:52

 
  Test
passed #74669
check fedora

00:14:39

 
  Full Builds
passed #74670
build android arm64 api28

00:02:50

passed #74671
build cerbero fedora x86_64

00:07:04