Slow cmake glob checks

On a cmake project that makes use of boost via `add_subdirectory`, the "Re-checking globbed directories..." stage at the start of the build will occasionally take several tens of seconds. This traces down to the use of `CONFIGURE_DEPENDS` on Boost.Assert and other Boost libraries.

https://github.com/boostorg/assert/blob/af15ced8d04907345a0211dab46557e085960eb7/CMakeLists.txt#L26

Consider disabling `CONFIGURE_DEPENDS` when Boost is used as a dependency, as glob results shouldn't change and re-checking can be costly.

Start with CMakeLists.txt around line 26 in Boost.Assert and inspect how CONFIGURE_DEPENDS is applied to globbed files. Reproduce the "Re-checking globbed directories..." delay in a CMake project using Boost through add_subdirectory, then verify that dependency builds no longer incur the costly re-check while normal glob behavior remains correct.

Written by the indexing model from the issue text.