- Remove the build_<platform> scripts that were simply calling cmake in favor of
using cmake directly
- Move flag CRT_SECURE_NO_WARNING into a section specifically for visual studio
- Change vendor file selection to just use the file if present
- Add a variable for determining whether to link against pthread
- Delete all lines in CMakeVendor.txt so each implementation can define their own
Change-Id: Ibbd83521ce4d42d09dcbd0b16efa9fbe6cbf785d