[gnome-applets] brightness: fix build

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 1ee719581c33d7d640ae9f656e4e9b192bafef78
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Wed Aug 8 18:12:33 2018 +0300

    brightness: fix build
    
    https://gitlab.gnome.org/GNOME/gnome-applets/issues/3

 brightness/src/Makefile.am | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/brightness/src/Makefile.am b/brightness/src/Makefile.am
index b1790e23b..56bcd3a55 100644
--- a/brightness/src/Makefile.am
+++ b/brightness/src/Makefile.am
@@ -17,6 +17,7 @@ libbrightness_applet_la_CPPFLAGS = \
 
 libbrightness_applet_la_CFLAGS = \
        $(GNOME_APPLETS_CFLAGS) \
+       $(GIO_UNIX_CFLAGS) \
        $(WARN_CFLAGS) \
        $(AM_CFLAGS) \
        $(NULL)
@@ -34,6 +35,7 @@ libbrightness_applet_la_LDFLAGS = \
 
 libbrightness_applet_la_LIBADD = \
        $(GNOME_APPLETS_LIBS) \
+       $(GIO_UNIX_LIBS) \
        $(NULL)
 
 BUILT_SOURCES = \