workflows: workaround Clang vs. Valgrind breakage
workflows: workaround Clang vs. Valgrind breakage

The latest version of Clang produces debugging output that's
incompatible with Valgrind.  Add a workaround for that.

See https://bugs.kde.org/show_bug.cgi?id=452758

martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit