cmLocalGenerator: Clarify GetIncludeFlags signature

Make the `config` argument non-optional so all callers must be explicit.
Convert the path style argument to an enumeration to make its role clear
at call sites.

The path style argument is implemented by `ConvertToIncludeReference`,
which was introduced with the Ninja generator by commit 5b114c9bee
(Introduce a cmLocalGenerator::ConvertToIncludeReference function,
2011-09-07, v2.8.7~187^2~4).  Its only purpose is to allow the Ninja
generator to use relative paths in `-I` flags.  Add a comment explaining
this role.

1 files changed, 6 insertions, 2 deletions

diff --git a/Source/cmGlobalXCodeGenerator.cxx b/Source/cmGlobalXCodeGenerator.cxx
index 8ecebae..37ef4fc 100644
--- a/Source/cmGlobalXCodeGenerator.cxx
+++ b/Source/cmGlobalXCodeGenerator.cxx
@@ -991,7 +991,10 @@ cmXCodeObject* cmGlobalXCodeGenerator::CreateXCodeSourceFile(
       includes, genexInterpreter.Evaluate(*cincludes, INCLUDE_DIRECTORIES),
       *sf);
   }
-  lg->AppendFlags(flags, lg->GetIncludeFlags(includes, gtgt, lang, true));
+  lg->AppendFlags(
+    flags,
+    lg->GetIncludeFlags(includes, gtgt, lang, std::string(), false,
+                        cmLocalGenerator::IncludePathStyle::Absolute));
 
   cmXCodeObject* buildFile =
     this->CreateXCodeBuildFileFromPath(sf->ResolveFullPath(), gtgt, lang, sf);
@@ -2695,7 +2698,8 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
     // GNU assembly files (#16449)
     for (auto const& language : languages) {
       std::string includeFlags = this->CurrentLocalGenerator->GetIncludeFlags(
-        includes, gtgt, language, true, false, configName);
+        includes, gtgt, language, configName, false,
+        cmLocalGenerator::IncludePathStyle::Absolute);
 
       if (!includeFlags.empty()) {
         cflags[language] += " " + includeFlags;