Tests: Add cache entries to control use of VCS tools by tests
Add undocumented CMake_TEST_ExternalProject_{CVS,SVN,GIT,HG}
cache entries to control use of VCS tools by the ExternalProject
test.
Add undocumented CMake_TEST_CTestUpdate_{CVS,SVN,GIT,HG,BZR,P4}
cache entries to explicitly enable or disable the CTest.Update{CVS,SVN,GIT,HG,BZR,P4}
tests.
If these are not defined, compute defaults as before. For BZR, the old logic was never enabling the test on current bzr
versions. Leave that one as opt-in only.
This gives nightly build maintainers control over what VCS tools are used from their environment.
Edited by Brad King