Following a suggestion by Ruslan, the initial creation of the
includes and libraries (and build tools) is now done by
invoking "make buildworld" (with -DPICOBSD which eventually will
limit the amount of stuff built with a 2-line change in Makefile.inc1).
The correct environment is then used for subsequent builds.
Also remove write_mfs_in_kernel.c in favour of using dd
All the above is conditional on __FreeBSD_version, as the previous
method still worked for versions earlier than 500035, and I am
unsure on how the "new" method works for earlier versions.
Finally, note that the crunch.conf files need some work because
some libraries (e.g. gmd) have gone away from the base installation.
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