.github: fix tetexec.cfg creation

We need to run the Xts build inside Xvfb, because it needs a running
Xserver for creating tetexec.cfg.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

.github/scripts/install-prereq.sh

@@ -16,6 +16,7 @@ build_ac      xorgproto         https://gitlab.freedesktop.org/xorg/proto/xorgpr
 if [ "$X11_OS" = "Darwin" ]; then
 build_ac      xset              https://gitlab.freedesktop.org/xorg/app/xset             xset-1.2.5
 fi
+# really must be build via autoconf instead of meson, otherwise piglit wont find the test programs
 build_ac_xts  xts               https://gitlab.freedesktop.org/xorg/test/xts             12a887c2c72c4258962b56ced7b0aec782f1ffed
 
 clone_source piglit             https://gitlab.freedesktop.org/mesa/piglit               28d1349844eacda869f0f82f551bcd4ac0c4edfe

.github/scripts/util.sh

@@ -79,6 +79,7 @@ build_ac_xts() {
     if [ -f $X11_PREFIX/$pkgname.DONE ]; then
         echo "package $pkgname already built"
     else
+        echo "::group::Build XTS"
         clone_source "$pkgname" "$url" "$ref"
         (
             cd $pkgname
@@ -103,8 +104,9 @@ build_ac_xts() {
                 fi
             fi
             ./autogen.sh --prefix=$X11_PREFIX CFLAGS="$CFLAGS"
-            make -j${FDO_CI_CONCURRENT:-4} install
+            xvfb-run make -j${FDO_CI_CONCURRENT:-4} install tetexec.cfg
         )
         touch $X11_PREFIX/$pkgname.DONE
+        echo "::endgroup::"
     fi
 }