PC-BSD/trueos 558e4cf. Makefile.inc1, lib Makefile

Initial commit to disable CLANG / LLVM building in world. Add a new
script clang-bootstrap which will be used to create links to the
version of llvm you want to use from ports (llvm60 default)
DeltaFile
+52-0usr.bin/clang-bootstrap/clang-bootstrap.sh
+11-0usr.bin/clang-bootstrap/Makefile.depend
+3-3lib/Makefile
+6-0Makefile.inc1
+5-0usr.bin/clang-bootstrap/Makefile
+2-2share/mk/src.opts.mk
+1-0usr.bin/Makefile
+80-57 files

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