cloog fails to build on MacOS Big Sur

[clegra]

--->  Fetching archive for cloog
--->  Attempting to fetch cloog-0.18.4_4.darwin_20.x86_64.tbz2 from http://fco.it.packages.macports.org/cloog
--->  Attempting to fetch cloog-0.18.4_4.darwin_20.x86_64.tbz2 from https://lil.fr.packages.macports.org/cloog
--->  Attempting to fetch cloog-0.18.4_4.darwin_20.x86_64.tbz2 from https://packages.macports.org/cloog
Warning: The macOS 11.2 SDK does not appear to be installed. Ports may not build correctly.
Warning: You can install it as part of the Xcode Command Line Tools package by running `xcode-select --install'.
--->  Computing dependencies for cloog
--->  Building cloog
Error: Failed to build cloog: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_devel_cloog/cloog/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.

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NB: I repeatedly checked the installation of Xcode, and the Xcode Command Line Tools, but the error seems not to be due to that, but the problem seems not to be resulting from there. This seems to be similar to ticket #62226 -- I take it from the answer there that this warning should be ignored for now.

[jmroot (Joshua Root)]

Could be #61488. Please attach the log.

[clegra]

logfile for the aborted installation of cloog