Can't build Chimera on OSX

To begin with, the pcre dependency is locked to 8.41 but 8.42 is now out. I changed the build script to require that version instead, but now I get:
```
CMake Warning (dev) at tools/hscollider/CMakeLists.txt:67 (add_dependencies):
Policy CMP0046 is not set: Error on non-existent dependency in
add_dependencies. Run "cmake --help-policy CMP0046" for policy details.
Use the cmake_policy command to set the policy and suppress this warning.

The dependency target "pcre" of target "hscollider" does not exist.
```
What else do I need to do?