export: Factor out CMake-specific export generation (2/2)

In order to support generation of Common Package Specifications, the
mechanisms CMake uses to export package information need to be made more
abstract. The prior commits began this refactoring; this continues by
(actually) restructuring the classes used to generate the actual export files.
To minimize churn, this introduces virtual base classes and
diamond inheritance in order to separate logic which is format-agnostic
but depends on the export mode (build-tree versus install-tree) from
logic which is format-specific but mode-agnostic.

This could probably be refactored further to use helper classes instead,
and a future commit may do that, however an initial attempt to do that
was proving even more invasive, such that this approach was deemed more
manageable.

While we're at it, add 'const' in more places where possible.

Source/cmExportInstallAndroidMKGenerator.h

@@ -5,9 +5,10 @@
 #include "cmConfigure.h" // IWYU pragma: keep
 
 #include <iosfwd>
-#include <set>
 #include <string>
+#include <vector>
 
+#include "cmExportAndroidMKGenerator.h"
 #include "cmExportInstallFileGenerator.h"
 #include "cmStateTypes.h"
 
@@ -15,52 +16,49 @@ class cmGeneratorTarget;
 class cmInstallExportGenerator;
 
 /** \class cmExportInstallAndroidMKGenerator
- * \brief Generate a file exporting targets from an install tree.
+ * \brief Generate files exporting targets from an install tree.
  *
  * cmExportInstallAndroidMKGenerator generates files exporting targets from
- * install an installation tree.  The files are placed in a temporary
- * location for installation by cmInstallExportGenerator.  The file format
- * is for the ndk build system and is a makefile fragment specifying prebuilt
- * libraries to the ndk build system.
+ * an installation tree.  The files are placed in a temporary location for
+ * installation by cmInstallExportGenerator.  The file format is for the ndk
+ * build system and is a makefile fragment specifying prebuilt libraries to the
+ * ndk build system.
  *
  * This is used to implement the INSTALL(EXPORT_ANDROID_MK) command.
  */
-class cmExportInstallAndroidMKGenerator : public cmExportInstallFileGenerator
+class cmExportInstallAndroidMKGenerator
+  : public cmExportAndroidMKGenerator
+  , public cmExportInstallFileGenerator
 {
 public:
   /** Construct with the export installer that will install the
       files.  */
   cmExportInstallAndroidMKGenerator(cmInstallExportGenerator* iegen);
 
+  std::string GetConfigImportFileGlob() const override { return {}; }
+
 protected:
+  GenerateType GetGenerateType() const override { return INSTALL; }
+
   // Implement virtual methods from the superclass.
-  void GeneratePolicyHeaderCode(std::ostream&) override {}
-  void GeneratePolicyFooterCode(std::ostream&) override {}
+  void ReportDuplicateTarget(std::string const& targetName) const;
+  bool GenerateMainFile(std::ostream& os) override;
   void GenerateImportHeaderCode(std::ostream& os,
                                 std::string const& config = "") override;
-  void GenerateImportFooterCode(std::ostream& os) override;
   void GenerateImportTargetCode(
     std::ostream& os, cmGeneratorTarget const* target,
     cmStateEnums::TargetType /*targetType*/) override;
-  void GenerateExpectedTargetsCode(
-    std::ostream& os, std::string const& expectedTargets) override;
-  void GenerateImportPropertyCode(
-    std::ostream& os, std::string const& config, std::string const& suffix,
-    cmGeneratorTarget const* target, ImportPropertyMap const& properties,
-    std::string const& importedXcFrameworkLocation) override;
-  void GenerateMissingTargetsCheckCode(std::ostream& os) override;
-  void GenerateFindDependencyCalls(std::ostream&) override {}
-  void GenerateInterfaceProperties(
-    cmGeneratorTarget const* target, std::ostream& os,
-    ImportPropertyMap const& properties) override;
-  void GenerateImportPrefix(std::ostream& os) override;
-  void LoadConfigFiles(std::ostream&) override;
-  void CleanupTemporaryVariables(std::ostream&) override;
-  void GenerateImportedFileCheckLoop(std::ostream& os) override;
-  void GenerateImportedFileChecksCode(
-    std::ostream& os, cmGeneratorTarget* target,
-    ImportPropertyMap const& properties,
-    std::set<std::string> const& importedLocations,
-    std::string const& importedXcFrameworkLocation) override;
-  bool GenerateImportFileConfig(std::string const& config) override;
+
+  void ComplainAboutMissingTarget(cmGeneratorTarget const* depender,
+                                  cmGeneratorTarget const* dependee,
+                                  std::vector<std::string> const& namespaces);
+
+  void GenerateImportTargetsConfig(std::ostream& os, std::string const& config,
+                                   std::string const& suffix) override
+  {
+    this->cmExportAndroidMKGenerator::GenerateImportTargetsConfig(os, config,
+                                                                  suffix);
+  }
+
+  std::string GetCxxModulesDirectory() const override { return {}; }
 };