elf-core: Remove SetTriple workaround

On FreeBSD I see that Arch, Vendor, OS, and Environment are unchanged
after this call (for x86_64, at least), and core debugging works without
it.

If we need to restore it we should be able to switch on
arch.GetTriple.getOS() instead of a compile-time #ifdef.

Thanks to Daniel Malea for testing on Linux.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186862 91177308-0d34-0410-b5e6-96231b3b80d8
elf-core: Run-time reg context selection

Instantiate RegisterContextCore... based on getOS() instead of with
compile-time #ifdef-ery.

The assert()s here are unfortunate, but better than crashing with no
explanation.  (This would previously happen for an unsupported
architecture, anyhow.)

We should add an equivalent OS and architecture test to
ProcessElfCore::DoLoadCore() and cleanly report the error to the user.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186865 91177308-0d34-0410-b5e6-96231b3b80d8
Fix i386 FreeBSD build


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@186871 91177308-0d34-0410-b5e6-96231b3b80d8