[totem] build: Fix detection of valac

[Bastien Nocera <hadess src gnome org>]

commit bfc31c4fca16effd9dda1a191130c80bd86a2117
Author: Bastien Nocera <hadess hadess net>
Date:   Mon Apr 27 13:32:58 2015 +0200

    build: Fix detection of valac
    
    AM_PROG_VALAC very helpfully sets $VALAC to:
    "Absolute path to the Vala compiler, or simply ‘valac’ if no suitable
    compiler Vala could be found at configure runtime."
    
    We were checking for $VALAC being empty, thus still trying to build Vala
    plugins even if Vala wasn't available.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 3ca032a..c3aca01 100644
--- a/configure.ac
+++ b/configure.ac
@@ -264,7 +264,7 @@ AC_ARG_ENABLE([vala],
 AC_MSG_RESULT([$enable_vala])
 if test "x$enable_vala" != "xno"; then
        AM_PROG_VALAC([$VALA_REQS])
-       if test "x$VALAC" = "x"; then
+       if test "$VALAC" = "valac"; then
                if test "x$enable_vala" = "xyes"; then
                        AC_MSG_ERROR([Vala plugin support explicitly requested, but not found])
                fi