TianoCore and the Python-based Build Process, Part 3

This is part III of my attempts to build the TianoCore EDK II with the Python-based tools. In order to circumvent the error that stopped me in part II, the build process needs to be taught to use GNU make, i.e. gmake, on FreeBSD instead of make, which is BSD make. This can be done by editing the *_ELFGCC_*_MAKE_PATH variable in Conf/tools_def.txt.

The tools_def.txt file is automatically copied from a template part of the BaseTools sources. This patch fixes the template so the changes described above do not have to be applied manually.

At this point, the build process starts and does actually build some modules. However, the UnixPkg cannot be built completely on FreeBSD. This is because the code makes some assumptions only true on Linux, e.g. the presence of the sys/vfs.h header.