On IRIX, dirname() and basename() are defined in -lgen.

security/nss/cmd/shlibsign/Makefile

@@ -60,6 +60,10 @@ else
     IS_WINDOWS="NO"
 endif
 
+ifeq ($(OS_TARGET), IRIX)
+    OS_LIBS += -lgen
+endif
+
 #
 # we really should have this driven from a list file made during the normal
 # NSS build prodecure.