installer: use the system proxy to download ViGEmBus if available

src_assets/windows/misc/vigembus/install-vigembus.bat

@@ -1,16 +1,33 @@
 @echo off
+setlocal enabledelayedexpansion
 
 rem Get temp directory
 set temp_dir=%temp%/Sunshine
 
 rem Create temp directory if it doesn't exist
 if not exist "%temp_dir%" mkdir "%temp_dir%"
 
+rem Get system proxy setting
+set proxy= 
+for /f "tokens=3" %%a in ('reg query "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings" ^| find /i "ProxyEnable"') do (
+  set ProxyEnable=%%a
+
+  if !ProxyEnable! equ 0x1 (
+  for /f "tokens=3" %%a in ('reg query "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings" ^| find /i "ProxyServer"') do (
+      set proxy=%%a
+      echo Using system proxy !proxy! to download ViGEmBus
+      set proxy=-x !proxy!
+    )
+  ) else (
+    rem Proxy is not enabled.
+  )
+)
+
 rem get browser_download_url from asset 0 of https://api.github.com/repos/vigem/vigembus/releases/latest
 set latest_release_url=https://api.github.com/repos/vigem/vigembus/releases/latest
 
 rem Use curl to get the api response, and find the browser_download_url
-for /F "tokens=* USEBACKQ" %%F in (`curl -s -L %latest_release_url% ^| findstr browser_download_url`) do (
+for /F "tokens=* USEBACKQ" %%F in (`curl -s !proxy! -L %latest_release_url% ^| findstr browser_download_url`) do (
   set browser_download_url=%%F
 )
 
@@ -23,7 +40,7 @@ set browser_download_url=%browser_download_url:browser_download_url: =%
 echo %browser_download_url%
 
 rem Download the exe
-curl -s -L -o "%temp_dir%\vigembus.exe" %browser_download_url%
+curl -s -L !proxy! -o "%temp_dir%\vigembus.exe" %browser_download_url%
 
 rem Install vigembus
 %temp_dir%\vigembus.exe /passive /promptrestart