flang-16, flang-17, flang-20, flang-devel: kernel panic while compiling

[ryandesign (Ryan Carsten Schmidt)]

Compiling flang-20 @20.1.8 caused the macOS 11 arm64 buildbot worker to kernel panic at step 6693 of 7650 three times in a row:

• ​https://build.macports.org/builders/ports-11_arm64-builder/builds/113496
• ​https://build.macports.org/builders/ports-11_arm64-builder/builds/113497
• ​https://build.macports.org/builders/ports-11_arm64-builder/builds/113498

[ryandesign (Ryan Carsten Schmidt)]

Instead of the usual crash log with backtrace, the crash reporter window only says:

SOCD report detected: (iBoot panic)

[ryandesign (Ryan Carsten Schmidt)]

Also happens with:

• flang-16: ​https://build.macports.org/builders/ports-11_arm64-builder/builds/116799/steps/install-port/logs/stdio
• flang-17: ​https://build.macports.org/builders/ports-11_arm64-builder/builds/116802/steps/install-port/logs/stdio

It's perhaps relevant that this machine also has macOS 15 on another volume in the same APFS container, and so "iBoot" has presumably been updated to a macOS 15-compatible and perhaps no longer entirely macOS 11-compatible version.

[ryandesign (Ryan Carsten Schmidt)]

Now reported to Apple as FB20004407.

[ryandesign (Ryan Carsten Schmidt)]

flang-17 didn't kernel panic after we set build.mem_per_job properly (#72954):

​https://build.macports.org/builders/ports-11_arm64-builder/builds/119631

flang-devel still kernel panics; we haven't set build.mem_per_job there (nor in flang-16):

​https://build.macports.org/builders/ports-11_arm64-builder/builds/119632