main, asm: Don't compile asm for tests on the host

The asm files use symbols in layout.ld, which won't exsist when tests
are run on the host (as it uses the host's linker script). This isn't an
issue for Rust code, as we have LTO enabled.

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

src/main.rs

@@ -38,6 +38,7 @@ mod pci;
 mod pe;
 mod virtio;
 
+#[cfg(not(test))]
 global_asm!(include_str!("asm/ram64.s"));
 
 extern "C" {