meson: Fix gstgl checks for qt and gtk

Also rename from build_ to have_, which is more accurate.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/587>

ext/gtk/meson.build

@@ -12,7 +12,8 @@ optional_deps = []
 
 gtk_dep = dependency('gtk+-3.0', required : get_option('gtk3'))
 if gtk_dep.found()
-  if build_gstgl and gstgl_dep.found() and gtk_dep.version().version_compare('>=3.15.0')
+  # FIXME: automagic
+  if have_gstgl and gtk_dep.version().version_compare('>=3.15.0')
     have_gtk3_gl_windowing = false
 
     if gst_gl_have_window_x11 and gst_gl_have_platform_glx

ext/qt/meson.build

@@ -26,7 +26,7 @@ if qt5_option.disabled()
   subdir_done()
 endif
 
-if not build_gstgl
+if not have_gstgl
   if qt5_option.enabled()
     error('qt5 qmlglsink plugin is enabled, but gstreamer-gl-1.0 was not found')
   endif

meson.build

@@ -273,9 +273,9 @@ gstvideo_dep = dependency('gstreamer-video-1.0', version : gst_req,
 gstgl_dep = dependency('gstreamer-gl-1.0', version : gst_req,
     fallback : ['gst-plugins-base', 'gstgl_dep'], required: false)
 
-build_gstgl = gstgl_dep.found() # FIXME: add option?
+have_gstgl = gstgl_dep.found()
 
-if build_gstgl
+if have_gstgl
   if gstgl_dep.type_name() == 'pkgconfig'
     gst_gl_apis = gstgl_dep.get_pkgconfig_variable('gl_apis').split()
     gst_gl_winsys = gstgl_dep.get_pkgconfig_variable('gl_winsys').split()

tests/examples/gtk/meson.build

@@ -4,7 +4,7 @@ executable('gtksink', 'gtksink.c',
   include_directories: [configinc],
   install: false)
 
-if build_gstgl
+if have_gstgl
   executable('gtkglsink', 'gtkglsink.c',
     dependencies: [gst_dep, gstgl_dep, gtk_dep, x11_dep],
     c_args: gst_plugins_good_args,