configure / meson: Move the GBM handling to meson.build

The GBM library detection does not need to be in the configure script,
since it does not have any user-facing options (there are no
--enable-gbm or --disable-gbm switches). Let's move it to meson.build
instead, so we don't have to clutter config-host.mak with the related
switches.

Additionally, only check for GBM if it is really required, i.e. if we
either compile with OpenGL or with virglrenderer support.

Message-Id: <20210714085045.797168-1-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

configure

@@ -3451,13 +3451,6 @@ esac
 ##########################################
 # opengl probe (for sdl2, gtk)
 
-gbm="no"
-if $pkg_config gbm; then
-    gbm_cflags="$($pkg_config --cflags gbm)"
-    gbm_libs="$($pkg_config --libs gbm)"
-    gbm="yes"
-fi
-
 if test "$opengl" != "no" ; then
   epoxy=no
   if $pkg_config epoxy; then
@@ -4688,13 +4681,6 @@ if test "$opengl" = "yes" ; then
   echo "OPENGL_LIBS=$opengl_libs" >> $config_host_mak
 fi
 
-if test "$gbm" = "yes" ; then
-    echo "CONFIG_GBM=y" >> $config_host_mak
-    echo "GBM_LIBS=$gbm_libs" >> $config_host_mak
-    echo "GBM_CFLAGS=$gbm_cflags" >> $config_host_mak
-fi
-
-
 if test "$avx2_opt" = "yes" ; then
   echo "CONFIG_AVX2_OPT=y" >> $config_host_mak
 fi

contrib/vhost-user-gpu/meson.build

@@ -1,6 +1,5 @@
-if 'CONFIG_TOOLS' in config_host and virgl.found() \
-    and 'CONFIG_GBM' in config_host and 'CONFIG_LINUX' in config_host \
-    and pixman.found()
+if 'CONFIG_TOOLS' in config_host and virgl.found() and gbm.found() \
+    and 'CONFIG_LINUX' in config_host and pixman.found()
   executable('vhost-user-gpu', files('vhost-user-gpu.c', 'virgl.c', 'vugbm.c'),
              dependencies: [qemuutil, pixman, gbm, virgl, vhost_user, opengl],
              install: true,

meson.build

@@ -472,11 +472,6 @@ if not get_option('zstd').auto() or have_block
                     required: get_option('zstd'),
                     method: 'pkg-config', kwargs: static_kwargs)
 endif
-gbm = not_found
-if 'CONFIG_GBM' in config_host
-  gbm = declare_dependency(compile_args: config_host['GBM_CFLAGS'].split(),
-                           link_args: config_host['GBM_LIBS'].split())
-endif
 virgl = not_found
 if not get_option('virglrenderer').auto() or have_system
   virgl = dependency('virglrenderer',
@@ -816,11 +811,17 @@ coreaudio = not_found
 if 'CONFIG_AUDIO_COREAUDIO' in config_host
   coreaudio = declare_dependency(link_args: config_host['COREAUDIO_LIBS'].split())
 endif
+
 opengl = not_found
 if 'CONFIG_OPENGL' in config_host
   opengl = declare_dependency(compile_args: config_host['OPENGL_CFLAGS'].split(),
                               link_args: config_host['OPENGL_LIBS'].split())
 endif
+gbm = not_found
+if (have_system or have_tools) and (virgl.found() or opengl.found())
+  gbm = dependency('gbm', method: 'pkg-config', required: false,
+                   kwargs: static_kwargs)
+endif
 
 gnutls = not_found
 gnutls_crypto = not_found
@@ -1244,6 +1245,7 @@ config_host_data.set('CONFIG_MPATH', mpathpersist.found())
 config_host_data.set('CONFIG_MPATH_NEW_API', mpathpersist_new_api)
 config_host_data.set('CONFIG_CURL', curl.found())
 config_host_data.set('CONFIG_CURSES', curses.found())
+config_host_data.set('CONFIG_GBM', gbm.found())
 config_host_data.set('CONFIG_GLUSTERFS', glusterfs.found())
 if glusterfs.found()
   config_host_data.set('CONFIG_GLUSTERFS_XLATOR_OPT', glusterfs.version().version_compare('>=4'))
@@ -3086,7 +3088,7 @@ summary_info += {'U2F support':       u2f.found()}
 summary_info += {'libusb':            libusb.found()}
 summary_info += {'usb net redir':     usbredir.found()}
 summary_info += {'OpenGL support':    config_host.has_key('CONFIG_OPENGL')}
-summary_info += {'GBM':               config_host.has_key('CONFIG_GBM')}
+summary_info += {'GBM':               gbm.found()}
 summary_info += {'libiscsi support':  libiscsi.found()}
 summary_info += {'libnfs support':    libnfs.found()}
 if targetos == 'windows'