Tracing tooling updates for 6.8-rc4

RTLA:
        - rtla tools are exiting with a positive value  when usage()
          is called. Make them return 0 if the usage was called via
          -h/--help.

        - the -P priority sets the sched priority for rtla workload.
          When the SCHED_OTHER scheduler is selected, it sets
          the rt_priority instead of the nice parameter. Setting
          the nice value is the correct thing, so fix it.

        - rtla is failing to compile with clang due to unsupported
          options from gcc. Adjusting the compiler/linker options
          makes clang work properly.

        - Remove the sched_getattr() unused function on utils.c.

        - Fixes on variable initialization and size, reported by
          clang.

Verification:
        - rv is failing to compile with clang due to unsupported
          options from gcc. Adjusting the compiler/linker options
          makes clang work properly.

        - Fix an uninitialized variable on in_kernel.c reported by
          clang.
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