- Fix reversed ccache version detection logic. Enable ccache support.
- Use '-pthread' for Clang. Clang supports '-pthread' on all BSDs except
for Darwin. [1]
Reported by: Achilleas Mantzios <achill@matrix.gatewaynet.com> [1]
Tested by: Achilleas Mantzios <achill@matrix.gatewaynet.com> [1]