[mutter/akitouni/cvt-native-backend: 2/2] build: check for cvt only when building the native backend (autotools)

[Abderrahim Kitouni <akitouni src gnome org>]

commit 04e1041c33ecac1478123f9e9203d4dc890c9a0c
Author: Abderrahim Kitouni <akitouni gnome org>
Date:   Sat Nov 10 10:01:31 2018 +0100

    build: check for cvt only when building the native backend (autotools)
    
    also error out properly when cvt is not found

 configure.ac | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index fdfaf614b..c762a89d6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -430,9 +430,11 @@ AC_CHECK_DECL([GL_EXT_x11_sync_object],
               [AC_MSG_ERROR([GL_EXT_x11_sync_object definition not found, please update your GL headers])],
               [#include <GL/glx.h>])
 
-AC_PATH_PROG([CVT],[cvt],[])
-if test x"$CVT" = xno; then
-  AC_MSG_ERROR([cvt not found in your path])
+if test "$have_native_backend" = yes; then
+  AC_PATH_PROG([CVT],[cvt],[])
+  if test x"$CVT" = x; then
+    AC_MSG_ERROR([cvt not found in your path])
+  fi
 fi
 
 #### Warnings (last since -Werror can disturb other tests)