Summary:
PIC is implied by BUILD_SHARED_LIBS in CMake, so the test is confusing.
Note that if one wants to build static and use it to create a shared library with it, he will need to compile either shared
or static with CMake option -DCMAKE_POSITION_INDEPENDENT_CODE
Closes https://github.com/facebook/folly/pull/833

Reviewed By: Orvid

Differential Revision: D7890111

Pulled By: yfeldblum

fbshipit-source-id: e3996cb83d30ae368dc5fdd4f55b721f7f89d0a0