On Fedora rawhide (34), valgrind gives a lot of warnings like:

    ./src/platform/tests/test-cleanup-linux.valgrind-log:--48279-- WARNING: unhandled amd64-linux syscall: 439
    ./src/platform/tests/test-cleanup-linux.valgrind-log:--48279-- You may be able to write your own handler.
    ./src/platform/tests/test-cleanup-linux.valgrind-log:--48279-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
    ./src/platform/tests/test-cleanup-linux.valgrind-log:--48279-- Nevertheless we consider this a bug.  Please report
    ./src/platform/tests/test-cleanup-linux.valgrind-log:--48279-- it at http://valgrind.org/support/bug_reports.html.

Ignore them.

(cherry picked from commit 2cb40f6e)
(cherry picked from commit 561bd7bb)
(cherry picked from commit 09b5a72b)
(cherry picked from commit e8155929)