VS: Make C++ module BMIs public by default for shared libraries

Enable the `AllProjectBMIsArePublic` option for shared libraries in the
VS project files when building with C++20 modules support.

.gitlab/ci/configure_windows_vs2022_x64.cmake

@@ -1,4 +1,4 @@
-set(CMake_TEST_MODULE_COMPILATION "named,partitions,internal_partitions" CACHE STRING "")
+set(CMake_TEST_MODULE_COMPILATION "named,partitions,internal_partitions,shared" CACHE STRING "")
 
 include("${CMAKE_CURRENT_LIST_DIR}/configure_windows_msvc_cxx_modules_common.cmake")
 include("${CMAKE_CURRENT_LIST_DIR}/configure_windows_vs_common.cmake")

Source/cmVisualStudio10TargetGenerator.cxx

@@ -793,6 +793,7 @@ void cmVisualStudio10TargetGenerator::WriteClassicMsBuildProjectFile(
     Elem(e0, "PropertyGroup").Attribute("Label", "UserMacros");
     this->WriteWinRTPackageCertificateKeyFile(e0);
     this->WritePathAndIncrementalLinkOptions(e0);
+    this->WritePublicProjectContentOptions(e0);
     this->WriteCEDebugProjectConfigurationValues(e0);
     this->WriteItemDefinitionGroups(e0);
     this->WriteCustomCommands(e0);
@@ -3115,6 +3116,29 @@ void cmVisualStudio10TargetGenerator::WritePathAndIncrementalLinkOptions(
   }
 }
 
+void cmVisualStudio10TargetGenerator::WritePublicProjectContentOptions(
+  Elem& e0)
+{
+  cmStateEnums::TargetType ttype = this->GeneratorTarget->GetType();
+  if (ttype != cmStateEnums::SHARED_LIBRARY) {
+    return;
+  }
+  if (this->ProjectType != VsProjectType::vcxproj) {
+    return;
+  }
+
+  Elem e1(e0, "PropertyGroup");
+  for (std::string const& config : this->Configurations) {
+    if (this->GeneratorTarget->HaveCxx20ModuleSources() &&
+        this->GeneratorTarget->HaveCxxModuleSupport(config) ==
+          cmGeneratorTarget::Cxx20SupportLevel::Supported) {
+      const std::string cond = this->CalcCondition(config);
+      // For DLL projects, we export all BMIs for now
+      e1.WritePlatformConfigTag("AllProjectBMIsArePublic", cond, "true");
+    }
+  }
+}
+
 void cmVisualStudio10TargetGenerator::OutputLinkIncremental(
   Elem& e1, std::string const& configName)
 {

Source/cmVisualStudio10TargetGenerator.h

@@ -97,6 +97,7 @@ private:
   void WriteWinRTPackageCertificateKeyFile(Elem& e0);
   void WriteXamlFilesGroup(Elem& e0);
   void WritePathAndIncrementalLinkOptions(Elem& e0);
+  void WritePublicProjectContentOptions(Elem& e0);
   void WriteItemDefinitionGroups(Elem& e0);
   void VerifyNecessaryFiles();
   void WriteMissingFiles(Elem& e1);