[CMake] Fail when Python interpreter doesn't match Python libraries version
[CMake] Fail when Python interpreter doesn't match Python libraries version

Because of how CMake finds the Python libraries and interpreter, it's
possible to end up with a discrepancy between the two. For example,
you'd end up using a Python 3 interpreter to run the test suite while
LLDB was built and linked against Python 2.

This patch adds a fatal error to CMake so we find out at configuration
time, instead of finding out at test time.

Differential revision: https://reviews.llvm.org/D64812

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@366243 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb