Am folowing this tutorial to compile Qt 4.8 with visual Studio 2013 but after running nmake i get:
C:\\Qt\\4.8.5.src\\src\\3rdparty\\javascriptcore\\JavaScriptCo
Your problem is that you do not use Visual Studio 2012 but 2013. VS 2012 is VS11 while VS 2013 is VS12 and your path "C:\Program Files (x86)\Microsoft Visual Studio 12.0" belongs to VS 2013.
The core problem however is that VS 2013 is C99 compliant which causes problems in the V8 engine and javascriptcore.
There is currently no solution but manual patching.