I gave up on running lldb as a sub-process (even after giving it permissions to attach, it causes lldb, debugserver, and Activity Monitor to hang with 100% CPU). Instead I use something like the above with /usr/bin/sample to get a backtrace when an assertion fails in my debug builds. (spindump must be run as root, so it is useless here)

@szymczyk thank you for the reference, but unfortunately that link points at a "Retired Document" (which in turn points at a newer page that is also obsolete (for Xcode 11.2) and that page points to https://developer.apple.com/documentation/xcode where MACOSX_DEPLOYMENT_TARGET does not seem to be present). I found a more direct reference at https://developer.apple.com/library/archive/documentation/DeveloperTools/Conceptual/cross_development/Configuring/configuring.html but that documentation, too, "is no longer being updated" and also refers to the newer, useless, documentation site. So, sofar I've had no luck in finding a current official documentation about how to do command line Makefile build.