build: glx: Lower gl version to work with libglvnd

When using mesa with libglvnd support, mesa will no longer install the
gl, glx, egl pkg-config files but instead let libglvnd provide them.
libglvnd maintainers decided to change the versioning as it was
mesa-specific previously. Now the libraries have versions of the API
they expose[1].
This causes problems when building the X server:

  checking for glproto >= 1.4.17 gl >= 9.2.0... no
  configure: error: Package requirements (glproto >= 1.4.17 gl >= 9.2.0) were not met:

  Requested 'gl >= 9.2.0' but version of gl is 1.2

Lower the version requirement to 1.2 to allow building against libglvnd
provided libraries

[1] 0dfaea2bcb

configure.ac

@@ -760,7 +760,7 @@ LIBDRI="dri >= 7.8.0"
 LIBDRM="libdrm >= 2.4.89"
 LIBEGL="egl"
 LIBGBM="gbm >= 10.2.0"
-LIBGL="gl >= 7.1.0"
+LIBGL="gl >= 1.2"
 LIBXEXT="xext >= 1.0.99.4"
 LIBXFONT="xfont2 >= 2.0.0"
 LIBXI="xi >= 1.2.99.1"
@@ -1115,7 +1115,7 @@ case "$DRI2,$HAVE_DRI2PROTO" in
 	yes,yes | auto,yes)
 		AC_DEFINE(DRI2, 1, [Build DRI2 extension])
 		DRI2=yes
-		LIBGL="gl >= 9.2.0"
+		LIBGL="gl >= 1.2"
 		SDK_REQUIRED_MODULES="$SDK_REQUIRED_MODULES $DRI2PROTO"
 		;;
 esac

glx/meson.build

@@ -39,7 +39,7 @@ if build_glx
             common_dep,
             dl_dep,
             dependency('glproto', version: '>= 1.4.17'),
-            dependency('gl', version: '>= 9.2.0'),
+            dependency('gl', version: '>= 1.2'),
         ],
         c_args: [
             glx_align64,