Don't use peercred.

Index: src/cpp/core/system/PosixUser.cpp
--- src/cpp/core/system/PosixUser.cpp.orig
+++ src/cpp/core/system/PosixUser.cpp
@@ -48,7 +48,7 @@ UserIdentity currentUserIdentity()
    return userIdentity;
 }
 
-#if defined(HAVE_SO_PEERCRED)
+#if defined(HAVE_SO_PEERCRED) && !defined(__OpenBSD__)
 
 Error socketPeerIdentity(int socket, UserIdentity* pIdentity)
 {
