Respect use-system-jpeg Qt setting

Forward the system-jpeg Qt setting to chromium.

Change-Id: I646176fdf6a1c7818828dc8b24543cc885cc3688
Reviewed-by: Andras Becsi <andras.becsi@theqtcompany.com>

src/core/config/desktop_linux.pri

@@ -16,4 +16,6 @@ GYP_CONFIG += \
     host_clang=0 \
     clang=0 \
 
+contains(QT_CONFIG, system-jpeg): GYP_CONFIG += use_system_libjpeg=1
+
 !contains(QT_CONFIG, pulseaudio): GYP_CONFIG += use_pulseaudio=0