[Differential] [Request, 52 lines] D1505: Enable building libclang_rt (asan, ubsan and profile) for selected arches

[dim (Dimitry Andric)]

dim created this revision.
dim added reviewers: andrew, bapt, emaste, imp.
dim added a subscriber: freebsd-toolchain.

REVISION SUMMARY
  I added the libclang_rt libraries (Address Sanitizer, Undefined Behavior
  Sanitizer and Profile Guided Optimization) from compiler-rt to the tree
  recently, but did not connect them to the build yet.
  
  The requirements for these libraries are:
  * Must be built with clang, gcc (not even recent versions) can build them
  * Only make sense to build when either the cross-tools stage (e.g. the
    stuff installed under ${WORLDTMP}) has clang enabled, or when then
    final world has clang enabled.
  * The sanitizer libraries can only be built for i386 and amd64.
  * The profile library can only be built for i386, amd64 and LE arm.
  
  Apart from the bit of ugliness in lib/Makefile (which Warner does not
  like), there is also still a practical problem, which I have not been
  able to solve as of yet:
  
  On amd64, the build32 stage will now build the libclang_rt libraries,
  but due to ${LIB32IMAKE} containing MK_TOOLCHAIN=no, the install32 stage
  will *not* install them.  I don't see any easy way around this, excect
  maybe partially reverting r264930, but that will get us back to the
  situation with NO_INCS, which Warner tried to avoid with that commit.
  
  Note that I also did not introduce yet another WITH_LIBCLANG_RT knob,
  since I don't really see the need: WITH_CLANG should basically always
  cause these libraries to be built and installed.
  
  However, if the general opinion is that another knob is good to have, I
  can implement it, and move the lib/Makefile ugliness to src.opts.mk
  instead.

TEST PLAN
  Build and install in various situations. Do a bunch of runtime tests to
  ascertain the asan, ubsan and profile libraries can be found when
  building programs with -fsanitize=address, -fsanitize=undefined and
  -fprofile-generate, respectively.

BRANCH
  /head

REVISION DETAIL
  https://reviews.freebsd.org/D1505

AFFECTED FILES
  etc/mtree/BSD.usr.dist
  lib/Makefile
  lib/libclang_rt/Makefile
  tools/build/mk/OptionalObsoleteFiles.inc

To: dim, andrew, bapt, emaste, imp
Cc: freebsd-toolchain