Merge branch 'pw/use-glibc-tunable-for-malloc-optim' into maint

Avoid repeatedly running getconf to ask libc version in the test suite, and instead just as it once per script. source: <pull.1311.git.1659620305757.gitgitgadget@gmail.com> * pw/use-glibc-tunable-for-malloc-optim: tests: cache glibc version check