Checking for any include below ${SRCTOP}/sys is too strict and breaks
e.g. mkimg which includes sys/sys/disk. ABI issues will only be caused
by including headers in sys/sys since they might not match the host.
Approved By: jhb (mentor)
Suggested By: imp
This can cause surprising errors if the build tools is built against
headers that don't match the host system. It is also required in order
to allow building on non-FreeBSD systems where the headers in
/usr/include/sys are usually completely incompatible with those in the
source tree.
I added an error to Makefile.boot if this is done and found this was
only the case in libnv. With this error in the Makefile ABI breakages
such as r336019 should no longer be possible.
Reviewed By: bdrewery, kevans
Approved By: jhb (mentor)
Differential Revision: https://reviews.freebsd.org/D16186
legacy stuff (binutils) depend on this order.
For this to work, provide (and use) specialized versions
of bsd.prog.mk and bsd.lib.mk that include the standard
versions first, then augment CFLAGS, DPADD, LDADD, and
LDFLAGS as necessary, with the legacy stuff.
Tested on: 4.0-RELEASE
