How to pin a package?

[Jeffrey Walton]

My old PowerMac G5 cannot build the CMake being supplied with
MacPorts. I know CMake now requires C+11 or C++14, and the antique
tools on the Mac do not meet the requirements. I want to pin CMake to
an older version for the Mac. For example, 3.15.4 or 3.14.6.

How do I pin a package using MacPorts?

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Here's what I have been experiencing for several months.

--->  Attempting to fetch cmake-3.16.5_0.darwin_9.ppc.tbz2 from
http://packages.macports.org/cmake
--->  Attempting to fetch cmake-3.16.5_0.darwin_9.ppc.tbz2 from
http://aus.us.packages.macports.org/macports/packages/cmake
--->  Attempting to fetch cmake-3.16.5_0.darwin_9.ppc.tbz2 from
http://mse.uk.packages.macports.org/sites/packages.macports.org/cmake
--->  Configuring cmake
Error: Failed to configure cmake: configure failure: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_devel_cmake/cmake/main.log
for details.
Error: Problem while installing cmake