Right now if ChildProcessMac.mm is compiled with internal SDKs on macOS >10.12 and deployed to macOS <=10.12 then the libsandbox private header will be used and sandbox_profile_t will be missing the char* trace field. We need to make sure that the redeclared version of sandbox_profile_t in SandboxSPI.h is used when compiling for a deployment target <=10.12.
I believe this is no longer relevant since sandbox caching is now disabled for < 10.13