Make build.bat return a proper errorcode if the build fails.

Author: mhagander

src/tools/msvc/build.bat

@@ -17,5 +17,8 @@ if "%CONFIG%" == "" set CONFIG=Debug
 
 if "%1" == "" msbuild pgsql.sln /verbosity:detailed /p:Configuration=%CONFIG%
 if not "%1" == "" vcbuild %1.vcproj %CONFIG%
+SET E=%ERRORLEVEL%
 
 cd %STARTDIR%
+
+exit /b %E%