[RaisingSpear]

Tangentially related, but I've had a case where GCC 9.4.0 shipped a broken arm_acle.h header [https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100985] - code which includes the header would always fail to compile.

Since users could be trying to compile it on GCC 9.4.0, and as the functionality dependent on the header isn't critical to the application, if the build detects the header is broken, it just disables the functionality and emits a warning.

Back to xz: If security isn't your top priority, it seems reasonable to just ignore the failure of an optional feature and just move along. Of course, in hindsight, it's easy to point fingers, but without that, it doesn't sound completely unreasonable to me.