libgcc9: Error: gcc9 9.5.0 is not supported on Darwin 17 i386

[WolfgangFahl (Wolfgang Fahl)]

sudo port upgrade outdated

ends with the following show stopper on my Mac Os High Sierra

--->  Computing dependencies for libgcc9
--->  Fetching archive for libgcc9
--->  Attempting to fetch libgcc9-9.5.0_2.darwin_17.x86_64.tbz2 from http://packages.macports.org/libgcc9
--->  Attempting to fetch libgcc9-9.5.0_2.darwin_17.x86_64.tbz2 from http://fra.de.packages.macports.org/libgcc9
--->  Attempting to fetch libgcc9-9.5.0_2.darwin_17.x86_64.tbz2 from http://ema.uk.packages.macports.org/libgcc9
--->  Fetching distfiles for libgcc9
Error: gcc9 9.5.0 is not supported on Darwin 17 i386
Error: Failed to fetch libgcc9: incompatible macOS version
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc9/libgcc9/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets if you believe there
is a bug.

I'd love to know how i can at least partly keep my system up-to date e.g. forcing to ignore/skip errors like this or find out which applications i might need to deinstall or install old versions from a dmg or the like.

[ryandesign (Ryan Carsten Schmidt)]

(lib)gcc9 is not supported on macOS High Sierra anymore. Use a newer version of (lib)gcc.

Since the problem happened when upgrading ports, figure out which of your installed ports depends on (lib)gcc9 and see if the port offers a variant to use a newer (lib)gcc instead.