[glib] build: Fix enable-libmount=auto

[Patrick Griffis <pgriffis src gnome org>]

commit b5e7e393950adeb9cd44f1e453a4411c9343b9be
Author: Patrick Griffis <tingping tingping se>
Date:   Wed Oct 11 18:21:24 2017 -0400

    build: Fix enable-libmount=auto

 meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/meson.build b/meson.build
index b38123d..efb4be3 100644
--- a/meson.build
+++ b/meson.build
@@ -1492,7 +1492,7 @@ libmount_opt = get_option('enable-libmount')
 if host_system == 'linux' and libmount_opt != 'no'
   libmount_dep = [dependency('mount', version : '>=2.28', required : false)]
   if not libmount_dep[0].found()
-    libmount_dep = [cc.find_library('mount')]
+    libmount_dep = [cc.find_library('mount', required : false)]
     libmount_h = cc.has_header('libmount/libmount.h')
     libmount_needed = libmount_opt == 'yes' and host_system == 'linux'
     if libmount_needed and (not libmount_dep[0].found() or not libmount_h)