[gvfs] build: Avoid running '1' as a command when systemd is not available

[Ondrej Holy <oholy src gnome org>]

commit 11481de51b6a364d3d9f0cfc62ef85f0cbfd7dda
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Wed May 10 22:17:27 2017 +0800

    build: Avoid running '1' as a command when systemd is not available
    
    The ACTION-IF-NOT-FOUND part of PKG_CHECK_MODULES is not needed and we
    can simply remove it to avoid the error here. This commit also replaces
    PKG_CHECK_MODULES with PKG_CHECK_EXISTS because variables set by
    PKG_CHECK_MODULES are not used.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=782442

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 82da91c..82191f3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -286,7 +286,7 @@ AC_ARG_WITH([systemduserunitdir],
 AC_SUBST([systemd_userdir])
 
 if test "x$systemd_userdir" != "xno"; then
-  PKG_CHECK_MODULES([SYSTEMD], [systemd >= 206], [msg_systemd_user_units=yes], 1)
+  PKG_CHECK_EXISTS([systemd >= 206], [msg_systemd_user_units=yes])
 fi
 
 AM_CONDITIONAL([USE_SYSTEMD_USER_UNITS], [test "$msg_systemd_user_units" = "yes"])