gcc11: build failure on macOS 11: Bootstrap comparison failure

[i0ntempest]

See buildbot log: ​https://build.macports.org/builders/ports-11_x86_64-builder/builds/41670/steps/install-port/logs/stdio

[mouse07410 (Mouse)]

Concur - same problem here. :-(

:info:build Comparing stages 2 and 3
:info:build warning: gcc/cc1obj-checksum.o differs
:info:build warning: gcc/cc1objplus-checksum.o differs
:info:build Bootstrap comparison failure!
:info:build gcc/jit/jit-recording.o differs
:info:build make[2]: *** [compare] Error 1
:info:build make[2]: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc11/gcc11/work/build'
:info:build make[1]: *** [stage3-bubble] Error 2
:info:build make[1]: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc11/gcc11/work/build'
:info:build make: *** [bootstrap-lean] Error 2
:info:build make: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc11/gcc11/work/build'
:info:build Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc11/gcc11/work/build" && /usr/bin/make -j20 -w bootstrap-lean 
:info:build Exit code: 2
:error:build Failed to build gcc11: command execution failed

Consistent on different machines (different CPUs, but all Intel and running macOS 11.5.1 with Xcode-12.5.1).

[i0ntempest]

Adding C expert Ken in to see if he got any ideas