chore: Mask ARM source if not AARCH64 not defined

runtime/include/arch/aarch64/context.h

@@ -1,4 +1,5 @@
 #pragma once
+#if defined(AARCH64) || defined(aarch64)
 
 #include <assert.h>
 #include "arch/common.h"
@@ -137,3 +138,7 @@ arch_context_switch(struct arch_context *a, struct arch_context *b)
 
 	return 0;
 }
+
+#else
+#warning "Neither AARCH64 nor aarch64 was defined, but aarch64/context.h was included!"
+#endif