Fix logic error buildscript bat file.

The string-contains check requires a not for it to be considered true
as the test is whether replacing the word in the string produces the same
result. If it does not then it is considered to be in the string.

Refs #9877

Code/Mantid/Build/Jenkins/buildscript.bat

@@ -46,10 +46,10 @@ if ERRORLEVEL 1 exit /B %ERRORLEVEL%
 :: Check the required build configuration
 :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
 set BUILD_CONFIG=
-if "%JOB_NAME%"=="%JOB_NAME:debug=%" (
+if not "%JOB_NAME%"=="%JOB_NAME:debug=%" (
     set BUILD_CONFIG=Debug
 ) else (
-if "%JOB_NAME%"=="%JOB_NAME:relwithdbg=%" (
+if not "%JOB_NAME%"=="%JOB_NAME:relwithdbg=%" (
     set BUILD_CONFIG=RelWithDbg
 ) else (
     set BUILD_CONFIG=Release