Revert "configure.ac: Use PKG_CHECK_VAR for wayland-scanner."

This reverts commit 8a26e94439.

configure.ac

@@ -2102,7 +2102,12 @@ if test "x$with_egl_platforms" != "x" -a "x$enable_egl" != xyes; then
     AC_MSG_ERROR([cannot build egl state tracker without EGL library])
 fi
 
-PKG_CHECK_VAR([WAYLAND_SCANNER], [wayland-scanner], [wayland_scanner])
+PKG_CHECK_MODULES([WAYLAND_SCANNER], [wayland-scanner],
+        WAYLAND_SCANNER=`$PKG_CONFIG --variable=wayland_scanner wayland-scanner`,
+        WAYLAND_SCANNER='')
+if test "x$WAYLAND_SCANNER" = x; then
+    AC_PATH_PROG([WAYLAND_SCANNER], [wayland-scanner])
+fi
 
 # Do per-EGL platform setups and checks
 egl_platforms=`IFS=', '; echo $with_egl_platforms`