OpenBSD neither provides nor requires librt.

Index: configure
--- configure.orig
+++ configure
@@ -267,7 +267,7 @@
   M += '\n'
   makefile = M + makefile
   M = 'package/bin/%s: command/%s.o%s.$(LIBcpucycles_VERSION)\n' % (base,base,''.join(' package/lib/%s.%s' % (x,linktype) for x in libs))
-  M += '\tcd command && ./link bin/%s %s.o%s.$(LIBcpucycles_VERSION) -lm -lrt\n' % (base,base,''.join(' lib/%s.%s' % (x,linktype) for x in libs))
+  M += '\tcd command && ./link bin/%s %s.o%s.$(LIBcpucycles_VERSION) -lm\n' % (base,base,''.join(' lib/%s.%s' % (x,linktype) for x in libs))
   M += '\n'
   makefile = M + makefile
   commands += ['package/bin/%s' % base]