In 664f345cd53d1f624d94f9889a1c9fff803e3391, a fix was introduced,
attempting to restore LLVM_DIR and Clang_DIR after doing
find_package(Clang).
However, 6775285e7695f2d45cf455f5d31b2c9fa9362d3d added a return if the
clangTidy target wasn't found. If this is hit, we don't restore LLVM_DIR
and Clang_DIR, which causes strange effects if CMake is rerun a second
time.
Move the code for restoring LLVM_DIR and Clang_DIR to directly after the
find_package calls, to make sure they are restored, regardless of the
find_package outcome.
51bceb46f8