update windows build script

Signed-off-by: R4SAS <r4sas@i2pmail.org>

build/build_mingw.cmd

@@ -52,9 +52,8 @@ REM converting configuration files to DOS format (make usable in Windows Notepad
 %xSH% "unix2dos contrib/i2pd.conf contrib/tunnels.conf contrib/tunnels.d/* contrib/webconsole/style.css" >> build\build.log 2>&1
 
 REM Prepare binary signing command if signing key and password provided
-if defined SIGNKEY (
-  if defined SIGNPASS (
-    echo Signing options found
+if defined SIGN (
+  echo Signing enabled
 
   for %%X in (signtool.exe) do (set xSIGNTOOL=%%~$PATH:X)
   if not defined xSIGNTOOL (
@@ -66,8 +65,15 @@ if defined SIGNKEY (
     )
   )
 
-    set "xSIGNOPTS=sign /tr http://timestamp.digicert.com /td sha256 /fd sha256 /f ^"%SIGNKEY%^" /p ^"%SIGNPASS%^""
+  if defined SIGNKEY (
+    set "xSIGNKEYOPTS=/f ^"%SIGNKEY%^""
   )
+
+  if defined SIGNPASS (
+    set "xSIGNPASSOPTS=/p ^"%SIGNPASS%^""
+  )
+
+  set "xSIGNOPTS=sign /tr http://timestamp.digicert.com /td sha256 /fd sha256 %SIGNKEYOPTS% %SIGNPASSOPTS%"
 )
 
 REM starting building