[gvfs] build: Bail if gphoto support is requested but not available

[Bastien Nocera <hadess src gnome org>]

commit 7d0127ee181c0b282b8f99f461d26fce1c3a27b0
Author: Arun Raghavan <arun accosted net>
Date:   Mon Apr 30 11:15:49 2012 +0100

    build: Bail if gphoto support is requested but not available
    
    https://bugzilla.gnome.org/show_bug.cgi?id=578027

 configure.ac |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index e55ab58..91621a9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -402,7 +402,7 @@ GPHOTO2_LIBS=
 GPHOTO2_CFLAGS=
 
 if test "x$enable_gphoto2" != "xno" -a \( "x$msg_hal" = "xyes" -o "x$msg_gudev" = "xyes" \); then
-  PKG_CHECK_EXISTS(libgphoto2, msg_gphoto2=yes)
+  PKG_CHECK_MODULES(GPHOTO2, libgphoto2 >= 2.4.0, [msg_gphoto2=yes])
 
   # Need OS tweaks in hal volume monitor backend
   case "$host" in
@@ -414,12 +414,19 @@ if test "x$enable_gphoto2" != "xno" -a \( "x$msg_hal" = "xyes" -o "x$msg_gudev"
       ;;
   esac
 
+  if test "x$enable_gphoto2" = "xyes" -a "x$msg_gphoto2" != "xyes"; then
+    AC_MSG_ERROR([gphoto2 support requested but not available])
+  fi
+
   if test "x$msg_gphoto2" = "xyes"; then
     if test "x$use_gphoto2" = "xyes"; then
-      PKG_CHECK_MODULES(GPHOTO2, libgphoto2 >= 2.4.0)
       AC_DEFINE(HAVE_GPHOTO2, 1, [Define to 1 if gphoto2 is available])
     else
-      AC_MSG_WARN([Not building with gphoto2 support. Need OS tweaks in hal volume monitor.])
+      if test "x$enable_gphoto2" = "xyes"; then
+        AC_MSG_ERROR([Cannot build with gphoto2 support. Need OS tweaks in hal volume monitor.])
+      else
+        AC_MSG_WARN([Not building with gphoto2 support. Need OS tweaks in hal volume monitor.])
+      fi
       msg_gphoto2=no
     fi
   fi