[gnome-boxes] flatpak: Build FreeRDP with OPENH264=ON

[Felipe Borges <felipeborges src gnome org>]

commit 6984f4112a7a84da3b224958450cef2ad6662145
Author: Felipe Borges <felipeborges gnome org>
Date:   Mon Apr 6 10:10:24 2020 +0200

    flatpak: Build FreeRDP with OPENH264=ON
    
    Otherwise freerdp will error out with:
    [ERROR][com.freerdp.codec] - Failed to create OpenH264 decoder
    [libopenh264 @ 0x7f3e84209500] Unable to create decoder
    [ERROR][com.freerdp.codec] - Failed to open libav codec
    [ERROR][com.freerdp.core.codecs] - Failed to create h264 codec context
    libfreerdp returned code is 00000000

 build-aux/flatpak/org.gnome.Boxes.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/build-aux/flatpak/org.gnome.Boxes.json b/build-aux/flatpak/org.gnome.Boxes.json
index ba97cef0..a1b94789 100644
--- a/build-aux/flatpak/org.gnome.Boxes.json
+++ b/build-aux/flatpak/org.gnome.Boxes.json
@@ -394,6 +394,7 @@
             "builddir": true,
             "config-opts": [
                 "-DCMAKE_BUILD_TYPE=RelWithDebInfo",
+                "-DWITH_OPENH264=ON",
                 "-DCMAKE_INSTALL_PREFIX=/app",
                 "-DCMAKE_INSTALL_LIBDIR=lib"
             ],