refactor: gate invariant_tsc module on x86_64

The invariant_tsc module uses core::arch::x86_64 intrinsics
(CPUID, RDTSC) which are not available on other architectures.

Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>

Author: ludfjig

src/hyperlight_guest_tracing/src/lib.rs

@@ -17,6 +17,7 @@ limitations under the License.
 #![no_std]
 
 /// Expose invariant TSC module
+#[cfg(target_arch = "x86_64")]
 pub mod invariant_tsc;
 
 /// Defines internal guest state