The configuration time suffers mostly on checking, which of the export tests
is to be reverted.
1.) There is a new configuration flag now, "LYX_ENABLE_EXOPRT_TESTS.
If not set (default) no export tests are created.
2.) If set, then the optimization halves the time needed for creation of tests.
The effect on my side:
a.) Until now the time was: ~ 26 seconds
b.) The optimized time is now: ~ 16 seconds
c.) With not enabled export tests: ~ 5 seconds
