add error check for qtcreator&netbeans project file generators to quit early if cmake fails.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53632 954f8c5b-7b00-dc11-b283-0030488c597c
Fix #33735: sequencer crash when using rendered preview

Issue was caused by preview job starting just moment before
sequencer starts rendering. This lead to threading conflicts
since renderer itself is not thread-safe.

Now all preview jobs would be killed before sequencer starts
rendering stack when final render for preview is enabled.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53633 954f8c5b-7b00-dc11-b283-0030488c597c