[gnome-control-center] build: Fix CUPS PPD deprecation warning

[Robert Ancell <rancell src gnome org>]

commit 96137369a5992721f5a3e543239bfa4a24431ff1
Author: Philip Chimento <philip endlessm com>
Date:   Fri Sep 13 18:00:41 2019 -0700

    build: Fix CUPS PPD deprecation warning
    
    In https://bugzilla.gnome.org/show_bug.cgi?id=696766 it was decided to
    build with _PPD_DEPRECATED defined, to suppress the warnings about the
    deprecation of the CUPS PPD API, since there was no full replacement
    yet. Unfortunately this didn't make it intact through the port to Meson,
    so fix it here.

 meson.build                 | 2 +-
 panels/printers/meson.build | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/meson.build b/meson.build
index 73cf43eb7..5c879a4a2 100644
--- a/meson.build
+++ b/meson.build
@@ -152,7 +152,7 @@ assert(cups_dep.found(), 'CUPS 1.4 or newer not found')
 # https://bugzilla.gnome.org/show_bug.cgi?id=696766
 cups_cflags = []
 if cups_dep.version().version_compare('>= 1.6')
-  cups_cflags += '-D_PPD_DEPRECATED=""'
+  cups_cflags += '-D_PPD_DEPRECATED='
 endif
 
 # cups headers
diff --git a/panels/printers/meson.build b/panels/printers/meson.build
index a1746a8e6..fa1ae99d5 100644
--- a/panels/printers/meson.build
+++ b/panels/printers/meson.build
@@ -69,7 +69,7 @@ printers_panel_lib = static_library(
   sources: sources,
   include_directories: [top_inc, common_inc, shell_inc],
   dependencies: deps,
-  c_args: cflags
+  c_args: cflags + cups_cflags,
 )
 panels_libs += [ printers_panel_lib ]