Using GLOB is slow and considered bad practice.

From https://cmake.org/cmake/help/latest/command/file.html:

> We do not recommend using GLOB to collect a list of source files from
> your source tree. If no CMakeLists.txt file changes when a source is
> added or removed then the generated build system cannot know when to ask
> CMake to regenerate. The CONFIGURE_DEPENDS flag may not work reliably on
> all generators, or if a new generator is added in the future that cannot
> support it, projects using it will be stuck. Even if CONFIGURE_DEPENDS
> works reliably, there is still a cost to perform the check on every
> rebuild.