We're parsing dmesg, just like FreeBSD

Index: include/cpu_features_macros.h
--- include/cpu_features_macros.h.orig
+++ include/cpu_features_macros.h
@@ -91,6 +91,10 @@
 #define CPU_FEATURES_OS_FREEBSD
 #endif
 
+#if (defined(__openbsd__) || defined(__OpenBSD__))
+#define CPU_FEATURES_OS_FREEBSD // currently the same
+#endif
+
 #if defined(__ANDROID__)
 #define CPU_FEATURES_OS_ANDROID
 #endif