gen_source.mk is a PSoC Creator generated source code.
This file should NOT be modified. It is automatically re-written by PSoC Creator as a part of the build process.
This file is written out for the toolchain selected in the export wizard. Later, it will be updated during each Build process, based on the current toolchain in the Build Settings. That is, if you export to Makefile and change from GCC to MDK, the Makefiles will likely not work. The gen_source.mk file will contain source code that is not supported by the toolchain in platform_debug.mk (or platform_release.mk). Either update the platform configuration file, or use the "Export to Makefile" feature to regenerate the files for the new toolchain.
CyComponentLibrary.a : this library is used to merge all components libraries in a single code object library.
So it will provide functions for all the components used in project.