Hide RdtscClock.h to non x86_64 builds

When testing the standalone build of public headers on ARM, the header Gaudi/Timers/RdtscClock.h fails because it is not supported on non-x86_64.

This MR tweaks the configuration to make sure Gaudi/Timers/RdtscClock.h is installed only for x86_64.

This MR, accidentally, fixes a minor inconsistency in some GaudiToolbox.cmake doc.

changed milestone to %v37r0

In this form, the MR effectively always disable the standalone test build for RdtscClock.h, but a proper fix requires some refactoring in GaudiToolbox.cmake.

marked this merge request as ready

added lhcb-gaudi-head label

assigned to @clemenci

• [2023-07-25 00:03] Validation started with lhcb-gaudi-head#3636
• [2023-07-25 00:18] Validation started with lhcb-run2-gaudi-head#588
• [2023-07-25 14:37] Validation started with lhcb-run2-gaudi-head#589

resolved all threads

mentioned in issue #271

approved this merge request

merged

mentioned in commit f0dee8e2

mentioned in merge request lhcb/Rec!3516 (merged)