runtime-rs: use pathBuf only for x86

PathBuf here is only used for x86.

Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>

src/runtime-rs/crates/hypervisor/src/ch/inner_hypervisor.rs

@@ -918,6 +918,7 @@ mod tests {
 
     use kata_types::config::hypervisor::{Hypervisor as HypervisorConfig, SecurityInfo};
     use serial_test::serial;
+    #[cfg(target_arch = "x86_64")]
     use std::path::PathBuf;
     use test_utils::{assert_result, skip_if_not_root};