cmInstallGenerator: Refactor computation of absolute install dest

Replace the GetInstallDestination method, which looked up the
Destination ivar, with a new ConvertToAbsoluteDestination method that
takes the nominal destination as an argument.  Update call sites
accordingly.  This will allow some clients to transform the install
destination before calling the method.

Source/cmInstallExportGenerator.cxx

@@ -199,7 +199,7 @@ void cmInstallExportGenerator::GenerateScriptActions(std::ostream& os,
 {
   // Remove old per-configuration export files if the main changes.
   std::string installedDir = "$ENV{DESTDIR}";
-  installedDir += this->GetInstallDestination();
+  installedDir += this->ConvertToAbsoluteDestination(this->Destination);
   installedDir += "/";
   std::string installedFile = installedDir;
   installedFile += this->FileName;

Source/cmInstallGenerator.cxx

@@ -60,7 +60,7 @@ void cmInstallGenerator
     case cmInstallType_FILES:          stype = "FILE"; break;
     }
   os << indent;
-  std::string dest = this->GetInstallDestination();
+  std::string dest = this->ConvertToAbsoluteDestination(this->Destination);
   if (cmSystemTools::FileIsFullPath(dest.c_str()))
      {
      os << "list(APPEND CMAKE_ABSOLUTE_DESTINATION_FILES\n";
@@ -179,15 +179,16 @@ bool cmInstallGenerator::InstallsForConfig(const std::string& config)
 }
 
 //----------------------------------------------------------------------------
-std::string cmInstallGenerator::GetInstallDestination() const
+std::string
+cmInstallGenerator::ConvertToAbsoluteDestination(std::string const& dest) const
 {
   std::string result;
-  if(!this->Destination.empty() &&
-     !cmSystemTools::FileIsFullPath(this->Destination.c_str()))
+  if(!dest.empty() &&
+     !cmSystemTools::FileIsFullPath(dest.c_str()))
     {
     result = "${CMAKE_INSTALL_PREFIX}/";
     }
-  result += this->Destination;
+  result += dest;
   return result;
 }
 

Source/cmInstallGenerator.h

@@ -52,7 +52,7 @@ public:
 
   /** Get the install destination as it should appear in the
       installation script.  */
-  std::string GetInstallDestination() const;
+  std::string ConvertToAbsoluteDestination(std::string const& dest) const;
 
   /** Test if this generator installs something for a given configuration.  */
   bool InstallsForConfig(const std::string& config);

Source/cmInstallTargetGenerator.cxx

@@ -77,7 +77,8 @@ void cmInstallTargetGenerator::GenerateScriptForConfig(std::ostream& os,
     fromDirConfig = this->Target->GetDirectory(config, this->ImportLibrary);
     fromDirConfig += "/";
     }
-  std::string toDir = this->GetInstallDestination();
+  std::string toDir =
+    this->ConvertToAbsoluteDestination(this->Destination);
   toDir += "/";
 
   // Compute the list of files to install for this target.