Reapply r332965 (by emaste):

lldb: remove assertion that target_arch is FreeBSD

The target is not necessarily a FreeBSD binary - for example, it may be
a Linux binary running under the linuxulator.  Basic ptrace (live)
debugging already worked in this case, except for the assertion.

Sponsored by:	Turing Robotic Industries Inc.

contrib/llvm-project/lldb/source/Plugins/Process/FreeBSD/FreeBSDThread.cpp

@@ -161,7 +161,6 @@ lldb::RegisterContextSP FreeBSDThread::GetRegisterContext() {
     RegisterInfoInterface *reg_interface = nullptr;
     const ArchSpec &target_arch = GetProcess()->GetTarget().GetArchitecture();
 
-    assert(target_arch.GetTriple().getOS() == llvm::Triple::FreeBSD);
     switch (target_arch.GetMachine()) {
     case llvm::Triple::aarch64:
       break;