If build in a prefix, define the system as prefix.

src/librc/librc.c

@@ -186,6 +186,10 @@ static bool file_regex (const char *file, const char *regex)
 
 const char *rc_sys (void)
 {
+#ifdef PREFIX
+	return (RC_SYS_PREFIX);
+#else	
+
 #ifdef __FreeBSD__
 	int jailed = 0;
 	size_t len = sizeof (jailed);
@@ -208,6 +212,7 @@ const char *rc_sys (void)
 #endif
 
 	return (NULL);
+#endif /* PREFIX */
 }
 
 static const char *rc_parse_service_state (rc_service_state_t state)

src/librc/rc.h

@@ -232,6 +232,7 @@ bool rc_service_daemons_crashed (const char *service);
  * OpenRC can support some special sub system types, normally virtualization.
  * Some services cannot work in these systems, or we do something else. */
 #define RC_SYS_JAIL    "JAIL"
+#define RC_SYS_PREFIX  "PREFIX"
 #define RC_SYS_UML     "UML"
 #define RC_SYS_VPS     "VPS"
 #define RC_SYS_XEN0    "XEN0"