Summary:
Only run cmake reconfigure for .cmake, .cmake.in and CMakeLists.txt
files changes.

Previously we would reconfigure for any change to a file with a path that
matched `cmake` which could result in false positives in cases where
you may be iterating on .py or .c files in shared cmake directories.

This also reclassifies non-cmake files under fbcode_builder/CMake as source
files so that we run cmake for those; previously they would cause a
reconfigure and build, now they just cause a build.

Reviewed By: xavierd

Differential Revision: D21364133

fbshipit-source-id: a1231f657d6c6056b269656c677d3449d8715cf6