Require SIGNTOOL_PARAMS to be set externally

scripts/build-arch.bat

@@ -26,6 +26,11 @@ if /I "%BUILD_CONFIG%"=="debug" (
                 exit /b 1
             )
 
+            if not defined SIGNTOOL_PARAMS (
+                echo "A signtool parameter string must be specified in SIGNTOOL_PARAMS for signed release builds"
+                exit /b 1
+            )
+
             echo Updating dependencies
             powershell %cd%\setup-deps.ps1
             if !ERRORLEVEL! NEQ 0 (
@@ -104,8 +109,6 @@ if not x%QT_PATH:_arm64=%==x%QT_PATH% (
 
 echo Detected target architecture: %ARCH%
 
-set SIGNTOOL_PARAMS=sign /tr http://timestamp.digicert.com /td sha256 /fd sha256 /sha1 8b9d0d682ad9459e54f05a79694bc10f9876e297 /v
-
 set BUILD_ROOT=%cd%\build
 set SOURCE_ROOT=%cd%
 set BUILD_FOLDER=%BUILD_ROOT%\build-%ARCH%-%BUILD_CONFIG%