RFR (XS) 8023406 - [windows] build_vm_def.sh takes too long even when BUILD_WIN_SA != 1

[Ioi Lam]

|Please review a very small fix:||
||
||http://cr.openjdk.java.net/~iklam/8023406/windows_build_vm_def_slow_001/||
||
||Bug: make/windows/build_vm_def.sh takes too long even when 
BUILD_WIN_SA != 1||
||
||http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8023406||
||    https://jbs.oracle.com/bugs/browse/JDK-8023406||
||
||Summary of fix:||
||
||    Reduce Windows build time to improve developer productivity.||
||
||    If BUILD_WIN_SA != 1, don't bother to generate vm.def, whose sole ||
||    purpose is for SA to determine the type information of C++ objects.||
||
||    Instead, this rather eye-catching warning is printed, and 10 seconds||
||    are saved in the build cycle.||
||
||        ***||
||        *** Not building SA: BUILD_WIN_SA != 1||
||        *** C++ Vtables NOT included in vm.def||
||        *** This jvm.dll will NOT work properly with SA.||
||        ***||
||        *** When in doubt, set BUILD_WIN_SA=1, clean and rebuild.||
||        ***||
||
||    This does not affect JPRT -- JPRT always sets BUILD_WIN_SA=1.||
||
||Result: ||
||
||    Touch 1 .cpp file; rebuild: Total time is reduced 15 seconds -> 5 
seconds.||
||
||Tests:||
||
     [0] Manual testing with both create.bat (IDE build) and build.bat
         VS 2008 + VS2010
||    [1] JPRT (windows.* only)||
||    [2] I built a jvm.dll without BUILD_WIN_SA=0, and it ran Eclipsed 
without||
||        any problem.||
||
||Thanks||
||- Ioi|