Do not place CMake version in export files

Files generated by `install(EXPORT)` and `export_library_dependencies()`
may be installed with packages and consumed by dependents.  In order to
avoid re-building dependents only because the version of CMake changed,
drop the CMake version from the export file content.

Source/cmExportFileGenerator.cxx

@@ -93,7 +93,7 @@ bool cmExportFileGenerator::GenerateImportFile()
 
   // Protect that file against use with older CMake versions.
   /* clang-format off */
-  os << "# Generated by CMake " << cmVersion::GetCMakeVersion() << "\n\n";
+  os << "# Generated by CMake\n\n";
   os << "if(\"${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}\" LESS 2.5)\n"
      << "   message(FATAL_ERROR \"CMake >= 2.6.0 required\")\n"
      << "endif()\n";

Source/cmExportLibraryDependenciesCommand.cxx

@@ -152,7 +152,7 @@ void cmExportLibraryDependenciesCommand::ConstFinalPass() const
   // versions.
   const char* vertest =
     "\"${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}\" GREATER 2.4";
-  fout << "# Generated by CMake " << cmVersion::GetCMakeVersion() << "\n\n";
+  fout << "# Generated by CMake\n\n";
   fout << "if(" << vertest << ")\n";
   fout << "  # Information for CMake 2.6 and above.\n";
   for (std::map<std::string, std::string>::const_iterator i =