cmake build needs to run tests AND collect results

CMake target "check-lldb" runs the lldb dotest.py suite, but doesn't
collect the results in a usable format. In adding the arguments
necessary to collect these results, I found some minor bugs in CMake
that prevented dotest overrides from being used. This patch fixes them.

<rdar://problem/33389717> cmake build needs to run tests AND collect results

llvm-svn: 308393