[cogl] configure: improve the error message if gbm missing

[Robert Bragg <rbragg src gnome org>]

commit 79ad416515b55ece8b9151876456555ff3fede2f
Author: Robert Bragg <robert linux intel com>
Date:   Wed Nov 27 20:38:00 2013 +0000

    configure: improve the error message if gbm missing
    
    This improves the error message in the case where libgbm is missing when
    the KMS egl platform has been enabled.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=706808
    
    Reviewed-by: Neil Roberts <neil linux intel com>

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 14f284d..a024234 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1081,7 +1081,7 @@ AS_IF([test "x$enable_kms_egl_platform" = "xyes"],
                            COGL_PKG_REQUIRES="$COGL_PKG_REQUIRES gbm"
                            COGL_PKG_REQUIRES="$COGL_PKG_REQUIRES libdrm"
                          ],
-                         [AC_MSG_ERROR([Unable to locate required kms libraries])])
+                         [AC_MSG_ERROR([Unable to locate required libgbm library for the KMS egl platform])])
 
         GBM_VERSION=`$PKG_CONFIG --modversion gbm`
         GBM_MAJOR=`echo $GBM_VERSION | cut -d'.' -f1`