selftests/bpf: __arch_* macro to limit test cases to specific archs

Add annotations __arch_x86_64, __arch_arm64, __arch_riscv64
to specify on which architecture the test case should be tested.
Several __arch_* annotations could be specified at once.
When test case is not run on current arch it is marked as skipped.

For example, the following would be tested only on arm64 and riscv64:

  SEC("raw_tp")
  __arch_arm64
  __arch_riscv64
  __xlated("1: *(u64 *)(r10 - 16) = r1")
  __xlated("2: call")
  __xlated("3: r1 = *(u64 *)(r10 - 16);")
  __success
  __naked void canary_arm64_riscv64(void)
  {
  	asm volatile (
  	"r1 = 1;"
  	"*(u64 *)(r10 - 16) = r1;"
  	"call %[bpf_get_smp_processor_id];"
  	"r1 = *(u64 *)(r10 - 16);"
  	"exit;"
  	:
  	: __imm(bpf_get_smp_processor_id)
  	: __clobber_all);
  }

On x86 it would be skipped:

  #467/2   verifier_nocsr/canary_arm64_riscv64:SKIP

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240722233844.1406874-10-eddyz87@gmail.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>