freebsd: Register JIT unwind info (JuliaLang#39581)

I noticed in JuliaLang#39553 that JIT unwind info didn't actually
work on FreeBSD. As a general policy, we should register our frame info to make sure
that our unwind is accurate. Libunwind has some heuristics to fall back to, but they
can break e.g. for large stack frames.

src/debuginfo.cpp

@@ -1244,7 +1244,7 @@ extern "C" jl_method_instance_t *jl_gdblookuplinfo(void *p) JL_NOTSAFEPOINT
     return jl_jit_events->lookupLinfo((size_t)p);
 }
 
-#if (defined(_OS_LINUX_) || (defined(_OS_DARWIN_) && defined(LLVM_SHLIB)))
+#if (defined(_OS_LINUX_) || defined(_OS_FREEBSD_) || (defined(_OS_DARWIN_) && defined(LLVM_SHLIB)))
 extern "C" void __register_frame(void*);
 extern "C" void __deregister_frame(void*);
 
@@ -1315,7 +1315,7 @@ void deregister_eh_frames(uint8_t *Addr, size_t Size)
     });
 }
 
-#elif defined(_OS_LINUX_) && \
+#elif (defined(_OS_LINUX_) || defined(_OS_FREEBSD_)) && \
     defined(JL_UNW_HAS_FORMAT_IP) && \
     !defined(_CPU_ARM_) // ARM does not have/use .eh_frame, so we handle this elsewhere
 #include <type_traits>