scons: Add warning for overloaded virtual functions

Fix the ISA startup warnings
diff --git a/src/arch/alpha/isa.hh b/src/arch/alpha/isa.hh
index 1832f02..e2e2dab 100644
--- a/src/arch/alpha/isa.hh
+++ b/src/arch/alpha/isa.hh
@@ -108,6 +108,9 @@
         ISA(Params *p);
 
         void startup(ThreadContext *tc) {}
+
+        /// Explicitly import the otherwise hidden startup
+        using SimObject::startup;
     };
 }
 
diff --git a/src/arch/arm/isa.hh b/src/arch/arm/isa.hh
index 12ecc49..e7abb26 100644
--- a/src/arch/arm/isa.hh
+++ b/src/arch/arm/isa.hh
@@ -195,6 +195,9 @@
 
         void startup(ThreadContext *tc) {}
 
+        /// Explicitly import the otherwise hidden startup
+        using SimObject::startup;
+
         typedef ArmISAParams Params;
 
         const Params *params() const;
diff --git a/src/arch/mips/isa.hh b/src/arch/mips/isa.hh
index 5ae779a..04d4a1d 100644
--- a/src/arch/mips/isa.hh
+++ b/src/arch/mips/isa.hh
@@ -159,6 +159,9 @@
       public:
         void startup(ThreadContext *tc) {}
 
+        /// Explicitly import the otherwise hidden startup
+        using SimObject::startup;
+
         const Params *params() const;
 
         ISA(Params *p);
diff --git a/src/arch/power/isa.hh b/src/arch/power/isa.hh
index f4e053d..33439c4 100644
--- a/src/arch/power/isa.hh
+++ b/src/arch/power/isa.hh
@@ -100,6 +100,9 @@
 
     void startup(ThreadContext *tc) {}
 
+    /// Explicitly import the otherwise hidden startup
+    using SimObject::startup;
+
     const Params *params() const;
 
     ISA(Params *p);
diff --git a/src/arch/sparc/isa.hh b/src/arch/sparc/isa.hh
index dac8a20..86092f3 100644
--- a/src/arch/sparc/isa.hh
+++ b/src/arch/sparc/isa.hh
@@ -173,6 +173,9 @@
 
     void startup(ThreadContext *tc) {}
 
+    /// Explicitly import the otherwise hidden startup
+    using SimObject::startup;
+
   protected:
 
     bool isHyperPriv() { return hpstate.hpriv; }
diff --git a/src/arch/x86/isa.hh b/src/arch/x86/isa.hh
index e87d747..3ccc2f0 100644
--- a/src/arch/x86/isa.hh
+++ b/src/arch/x86/isa.hh
@@ -88,6 +88,10 @@
         void serialize(std::ostream &os);
         void unserialize(Checkpoint *cp, const std::string &section);
         void startup(ThreadContext *tc);
+
+        /// Explicitly import the otherwise hidden startup
+        using SimObject::startup;
+
     };
 }