update the signing script to avoid racing when building in parallel

cert/sign_helper.bat

@@ -13,9 +13,14 @@ if not defined file (
 pushd "%~dp0"
 set "OPENSSL_CONF=%cd%\openssl.cnf"
 
-set "pvt_file=%cd%\prvt.pem"
-set "cer_file=%cd%\cert.pem"
-set "pfx_file=%cd%\cfx.pfx"
+call :gen_rnd rr
+set "pvt_file=%cd%\prvt-%rr%.pem"
+
+call :gen_rnd rr
+set "cer_file=%cd%\cert-%rr%.pem"
+
+call :gen_rnd rr
+set "pfx_file=%cd%\cfx-%rr%.pfx"
 
 set "openssl_exe=%cd%\openssl.exe"
 set "signtool_exe=%cd%\signtool.exe"
@@ -41,13 +46,14 @@ if %exit% neq 0 (
 
 call "%openssl_exe%" pkcs12 -export -out "%pfx_file%" -inkey "%pvt_file%" -in "%cer_file%" -passout pass:
 set /a exit+=%errorlevel%
-if %exit% neq 0 (
-  goto :end_script
-)
 
 del /f /q "%cer_file%"
 del /f /q "%pvt_file%"
 
+if %exit% neq 0 (
+  goto :end_script
+)
+
 call "%signtool_exe%" sign /d "GSE" /fd sha256 /f "%pfx_file%" /p "" "%~1"
 set /a exit+=%errorlevel%
 if %exit% neq 0 (
@@ -59,3 +65,18 @@ del /f /q "%pfx_file%"
 :end_script
 endlocal
 exit /b %exit%
+
+
+:: when every project is built in parallel '/MP' with Visual Studio,
+:: the regular random variable might be the same, causing racing
+:: this will waste some time and hopefully generate a different number
+:: 1: (ref) out random number
+:gen_rnd
+  setlocal enabledelayedexpansion 
+  for /l %%A in (1, 1, 100) do (
+    set "_r=!random!"
+  )
+endlocal & (
+  set "%~1=%random%"
+  exit /b
+)