Anyone building HHVM for install in /usr/local should get this patch first:

https://github.com/hhvm/hhvm-third-party/pull/39

Before that change, installation would put a broken libpcre.a into /usr/local/lib, which would then be used in subsequent builds. Hence the errors "this version of PCRE is compiled without UTF support" we were seeing yesterday.

FindPCRE.cmake would only enable unicode support in the bundled library if it was actually going to link against it. So if there was a system library available, it would compile and install the bundled library with the default configuration.

-- Tim Starling