cmGeneratorTarget: Factor link interface/impl methods into own source

Source/CMakeLists.txt

@@ -287,6 +287,7 @@ add_library(
   cmGeneratorTarget.h
   cmGeneratorTarget_CompatibleInterface.cxx
   cmGeneratorTarget_IncludeDirectories.cxx
+  cmGeneratorTarget_Link.cxx
   cmGeneratorTarget_LinkDirectories.cxx
   cmGeneratorTarget_Options.cxx
   cmGeneratorTarget_Sources.cxx

Source/cmGeneratorTarget.h

@@ -18,7 +18,6 @@
 #include <cm/string_view>
 
 #include "cmAlgorithms.h"
-#include "cmComputeLinkInformation.h"
 #include "cmLinkItem.h"
 #include "cmListFileCache.h"
 #include "cmPolicies.h"
@@ -29,6 +28,7 @@
 class cmake;
 enum class cmBuildStep;
 class cmCompiledGeneratorExpression;
+class cmComputeLinkInformation;
 class cmCustomCommand;
 class cmFileSet;
 class cmGlobalGenerator;

bootstrap

@@ -383,6 +383,7 @@ CMAKE_CXX_SOURCES="\
   cmGeneratorTarget \
   cmGeneratorTarget_CompatibleInterface \
   cmGeneratorTarget_IncludeDirectories \
+  cmGeneratorTarget_Link \
   cmGeneratorTarget_LinkDirectories \
   cmGeneratorTarget_Options \
   cmGeneratorTarget_Sources \