VS: Add method to re-parse specific option parser fields

This will allow a client to parse flags, replace the flag tables, and
then re-parse a field in which flags for a secondary tool were
collected.

Source/cmVisualStudioGeneratorOptions.cxx

@@ -43,6 +43,8 @@ cmVisualStudioGeneratorOptions::cmVisualStudioGeneratorOptions(
   this->FortranRuntimeDebug = false;
   this->FortranRuntimeDLL = false;
   this->FortranRuntimeMT = false;
+
+  this->UnknownFlagField = "AdditionalOptions";
 }
 
 cmVisualStudioGeneratorOptions::cmVisualStudioGeneratorOptions(
@@ -67,6 +69,8 @@ cmVisualStudioGeneratorOptions::cmVisualStudioGeneratorOptions(
   this->FortranRuntimeDebug = false;
   this->FortranRuntimeDLL = false;
   this->FortranRuntimeMT = false;
+
+  this->UnknownFlagField = "AdditionalOptions";
 }
 
 void cmVisualStudioGeneratorOptions::AddTable(cmVS7FlagTable const* table)
@@ -229,6 +233,18 @@ void cmVisualStudioGeneratorOptions::PrependInheritedString(
   value = "%(" + key + ") " + value;
 }
 
+void cmVisualStudioGeneratorOptions::Reparse(std::string const& key)
+{
+  std::map<std::string, FlagValue>::iterator i = this->FlagMap.find(key);
+  if (i == this->FlagMap.end() || i->second.size() != 1) {
+    return;
+  }
+  std::string const original = i->second[0];
+  i->second[0] = "";
+  this->UnknownFlagField = key;
+  this->Parse(original.c_str());
+}
+
 void cmVisualStudioGeneratorOptions::StoreUnknownFlag(const char* flag)
 {
   // Look for Intel Fortran flags that do not map well in the flag table.
@@ -255,7 +271,7 @@ void cmVisualStudioGeneratorOptions::StoreUnknownFlag(const char* flag)
   std::string const opts = cmOutputConverter::EscapeWindowsShellArgument(
     flag, cmOutputConverter::Shell_Flag_AllowMakeVariables |
       cmOutputConverter::Shell_Flag_VSIDE);
-  this->AppendFlagString("AdditionalOptions", opts);
+  this->AppendFlagString(this->UnknownFlagField, opts);
 }
 
 void cmVisualStudioGeneratorOptions::SetConfiguration(const char* config)

Source/cmVisualStudioGeneratorOptions.h

@@ -52,6 +52,10 @@ public:
 
   void PrependInheritedString(std::string const& key);
 
+  // Parse the content of the given flag table entry again to extract
+  // known flags and leave the rest in the original entry.
+  void Reparse(std::string const& key);
+
   // Fix the ExceptionHandling option to default to off.
   void FixExceptionHandlingDefault();
 
@@ -84,6 +88,8 @@ private:
   bool FortranRuntimeDLL;
   bool FortranRuntimeMT;
 
+  std::string UnknownFlagField;
+
   virtual void StoreUnknownFlag(const char* flag);
 };