Ninja: add properties for Swift partial module and doc

When building a swift object, we emit a partial swiftmodule and swiftdoc
that must be merged at the end.  However, in order to do that, we need
to enumerate the swiftmodules and swiftdocs.  As a result, the path must
be known to CMake.  Rather than hardcoding the rules into CMake, create
a source property that we can query.  This will allow us to create a
final placeholder to emit the merge rule.

Issue: #18800

Source/cmNinjaTargetGenerator.cxx

@@ -455,6 +455,8 @@ void cmNinjaTargetGenerator::WriteCompileRule(const std::string& lang)
     vars.SwiftAuxiliarySources = "$SWIFT_AUXILIARY_SOURCES";
     vars.SwiftModuleName = "$SWIFT_MODULE_NAME";
     vars.SwiftLibraryName = "$SWIFT_LIBRARY_NAME";
+    vars.SwiftPartialModule = "$SWIFT_PARTIAL_MODULE";
+    vars.SwiftPartialDoc = "$SWIFT_PARTIAL_DOC";
   }
 
   // For some cases we do an explicit preprocessor invocation.
@@ -945,6 +947,18 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatement(
     cmGeneratorTarget::Names targetNames =
       this->GeneratorTarget->GetLibraryNames(this->GetConfigName());
     vars["SWIFT_LIBRARY_NAME"] = targetNames.Base;
+
+    if (const char* partial = source->GetProperty("SWIFT_PARTIAL_MODULE")) {
+      vars["SWIFT_PARTIAL_MODULE"] = partial;
+    } else {
+      vars["SWIFT_PARTIAL_MODULE"] = objectFileName + ".swiftmodule";
+    }
+
+    if (const char* partial = source->GetProperty("SWIFT_PARTIAL_DOC")) {
+      vars["SWIFT_PARTIAL_DOC"] = partial;
+    } else {
+      vars["SWIFT_PARTIAL_DOC"] = objectFileName + ".swiftdoc";
+    }
   }
 
   if (!this->NeedDepTypeMSVC(language)) {

Source/cmRulePlaceholderExpander.cxx

@@ -177,6 +177,16 @@ std::string cmRulePlaceholderExpander::ExpandRuleVariable(
       return replaceValues.SwiftLibraryName;
     }
   }
+  if (replaceValues.SwiftPartialDoc) {
+    if (variable == "SWIFT_PARTIAL_DOC") {
+      return replaceValues.SwiftPartialDoc;
+    }
+  }
+  if (replaceValues.SwiftPartialModule) {
+    if (variable == "SWIFT_PARTIAL_MODULE") {
+      return replaceValues.SwiftPartialModule;
+    }
+  }
   if (variable == "TARGET_SONAME" || variable == "SONAME_FLAG" ||
       variable == "TARGET_INSTALLNAME_DIR") {
     // All these variables depend on TargetSOName

Source/cmRulePlaceholderExpander.h

@@ -61,6 +61,8 @@ public:
     const char* SwiftAuxiliarySources;
     const char* SwiftModuleName;
     const char* SwiftLibraryName;
+    const char* SwiftPartialModule;
+    const char* SwiftPartialDoc;
   };
 
   // Expand rule variables in CMake of the type found in language rules