systemc: Add the nonstandard time_stamp function.

Change-Id: I608c390b125611e5b62483c7e8567bb5479df553
Reviewed-on: https://gem5-review.googlesource.com/11281
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/systemc/channel/sc_clock.cc

@@ -107,6 +107,13 @@ sc_clock::posedge_first() const
     return false;
 }
 
+const sc_time &
+sc_clock::time_stamp()
+{
+    warn("%s not implemented.\n", __PRETTY_FUNCTION__);
+    return *(const sc_time *)nullptr;
+}
+
 const char *sc_clock::kind() const { return "sc_clock"; }
 
 void sc_clock::before_end_of_elaboration() {}

src/systemc/ext/channel/sc_clock.hh

@@ -71,6 +71,9 @@ class sc_clock : public sc_signal<bool>
     const sc_time &start_time() const;
     bool posedge_first() const;
 
+    // Nonstandard
+    static const sc_time &time_stamp();
+
     virtual const char *kind() const;
 
   protected: