ruby30: won't install on Mac OS X 10.12.6

[simon-dedeo]

with MacPorts version 2.6.4

simon$ sudo port install ruby30
--->  Computing dependencies for ruby30
--->  Fetching archive for ruby30
--->  Attempting to fetch ruby30-3.0.0_0.darwin_16.x86_64.tbz2 from https://ywg.ca.packages.macports.org/mirror/macports/packages/ruby30
--->  Attempting to fetch ruby30-3.0.0_0.darwin_16.x86_64.tbz2 from https://mse.uk.packages.macports.org/ruby30
--->  Attempting to fetch ruby30-3.0.0_0.darwin_16.x86_64.tbz2 from https://lil.fr.packages.macports.org/ruby30
--->  Fetching distfiles for ruby30
--->  Verifying checksums for ruby30
--->  Extracting ruby30
--->  Configuring ruby30
--->  Building ruby30
Error: Failed to build ruby30: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_ruby30/ruby30/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
Error: Processing of port ruby30 failed

Oddly, my particular version of Mac OS X (10.12) is flagged as bad at ​https://ports.macports.org/port/ruby30/summary

Thank you for any help -- keen to get our code up and running on the new system.

[simon-dedeo]

logfile output from ports ("Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_ruby30/ruby30/main.log for details")