[PATCH xserver] meson: Fix building with -Ddga=false

[Lyude Paul]

We forget to assign a value to xf86dgaproto_dep if -Ddga=false, which
causes the meson build to fail:

meson.build:448:0: ERROR:  Unknown variable "xf86dgaproto_dep".

A full log can be found at /home/lyudess/build/xserver/meson-logs/meson-log.txt
FAILED: build.ninja

So, just set it to an empty dependency to fix that.

Signed-off-by: Lyude Paul <lyude at redhat.com>
---
 meson.build | 1 +
 1 file changed, 1 insertion(+)

diff --git a/meson.build b/meson.build
index 53cdbe2be..29794f083 100644
--- a/meson.build
+++ b/meson.build
@@ -407,6 +407,7 @@ if not build_xv
 endif
 
 build_dga = false
+xf86dgaproto_dep = dependency('', required: false)
 if get_option('dga') == 'auto'
     xf86dgaproto_dep = dependency('xf86dgaproto', version: '>= 2.0.99.1', required: false)
     if xf86dgaproto_dep.found()
-- 
2.17.1