Add /opt/local/lib as a search path for gpg-error

Why doesn't WAF just search LD_LIBRARY_PATH?

wscript

@@ -133,7 +133,7 @@ def configure(conf):
                     #libpath=['/usr/lib', '/usr/local/lib'],
                     uselib_store='GNUTLS'):
     if conf.check(lib='gpg-error',
-                  libpath=['/usr/lib', '/usr/local/lib'],
+                  libpath=['/usr/lib', '/usr/local/lib', '/opt/local/lib'],
                   uselib_store='GPGERROR'):
       conf.env.append_value("CCFLAGS", "-DEVCOM_HAVE_GNUTLS=1")
       conf.env.append_value("CXXFLAGS", "-DEVCOM_HAVE_GNUTLS=1")