cmLocalGenerator: Add a hook for compiler flags used at link time

When using a compiler to drive linking we add compiler flags from
`CMAKE_<LANG>_FLAGS` in case they affect the way the compiler invokes
the linker, but we don't add flags from other places that are meant only
for compiling sources.  Rather than calling the `AddLanguageFlags`
method (which is used to add flags for compiling sources) directly, add
an intermediate method that is used when adding the flags for linking.
This will give us a way to add language-specific compiler flags needed
when driving the linker in the same place on the command line as other
compiler flags go.

Source/cmLocalGenerator.cxx

@@ -1002,7 +1002,7 @@ void cmLocalGenerator::GetTargetFlags(
           target->GetName().c_str());
         return;
       }
-      this->AddLanguageFlags(flags, target, linkLanguage, buildType);
+      this->AddLanguageFlagsForLinking(flags, target, linkLanguage, buildType);
       if (pcli) {
         this->OutputLinkLibraries(pcli, linkLineComputer, linkLibs,
                                   frameworkPath, linkPath);
@@ -1317,6 +1317,13 @@ void cmLocalGenerator::AddLanguageFlags(std::string& flags,
   }
 }
 
+void cmLocalGenerator::AddLanguageFlagsForLinking(
+  std::string& flags, cmGeneratorTarget const* target, const std::string& lang,
+  const std::string& config)
+{
+  this->AddLanguageFlags(flags, target, lang, config);
+}
+
 cmGeneratorTarget* cmLocalGenerator::FindGeneratorTargetToUse(
   const std::string& name) const
 {

Source/cmLocalGenerator.h

@@ -102,6 +102,10 @@ public:
 
   void AddLanguageFlags(std::string& flags, cmGeneratorTarget const* target,
                         const std::string& lang, const std::string& config);
+  void AddLanguageFlagsForLinking(std::string& flags,
+                                  cmGeneratorTarget const* target,
+                                  const std::string& lang,
+                                  const std::string& config);
   void AddCMP0018Flags(std::string& flags, cmGeneratorTarget const* target,
                        std::string const& lang, const std::string& config);
   void AddVisibilityPresetFlags(std::string& flags,

Source/cmMakefileExecutableTargetGenerator.cxx

@@ -150,8 +150,8 @@ void cmMakefileExecutableTargetGenerator::WriteDeviceExecutableRule(
                                       linkLanguage, *this->GeneratorTarget));
 
   // Add language feature flags.
-  this->LocalGenerator->AddLanguageFlags(flags, this->GeneratorTarget,
-                                         linkLanguage, this->ConfigName);
+  this->LocalGenerator->AddLanguageFlagsForLinking(
+    flags, this->GeneratorTarget, linkLanguage, this->ConfigName);
 
   this->LocalGenerator->AddArchitectureFlags(flags, this->GeneratorTarget,
                                              linkLanguage, this->ConfigName);
@@ -434,8 +434,8 @@ void cmMakefileExecutableTargetGenerator::WriteExecutableRule(bool relink)
   }
 
   // Add language feature flags.
-  this->LocalGenerator->AddLanguageFlags(flags, this->GeneratorTarget,
-                                         linkLanguage, this->ConfigName);
+  this->LocalGenerator->AddLanguageFlagsForLinking(
+    flags, this->GeneratorTarget, linkLanguage, this->ConfigName);
 
   this->LocalGenerator->AddArchitectureFlags(flags, this->GeneratorTarget,
                                              linkLanguage, this->ConfigName);

Source/cmMakefileLibraryTargetGenerator.cxx

@@ -397,8 +397,8 @@ void cmMakefileLibraryTargetGenerator::WriteDeviceLibraryRules(
 
     // Add language-specific flags.
     std::string langFlags;
-    this->LocalGenerator->AddLanguageFlags(langFlags, this->GeneratorTarget,
-                                           linkLanguage, this->ConfigName);
+    this->LocalGenerator->AddLanguageFlagsForLinking(
+      langFlags, this->GeneratorTarget, linkLanguage, this->ConfigName);
 
     vars.LanguageCompileFlags = langFlags.c_str();
 
@@ -858,8 +858,8 @@ void cmMakefileLibraryTargetGenerator::WriteLibraryRules(
 
     // Add language-specific flags.
     std::string langFlags;
-    this->LocalGenerator->AddLanguageFlags(langFlags, this->GeneratorTarget,
-                                           linkLanguage, this->ConfigName);
+    this->LocalGenerator->AddLanguageFlagsForLinking(
+      langFlags, this->GeneratorTarget, linkLanguage, this->ConfigName);
 
     this->LocalGenerator->AddArchitectureFlags(
       langFlags, this->GeneratorTarget, linkLanguage, this->ConfigName);

Source/cmNinjaNormalTargetGenerator.cxx

@@ -655,7 +655,8 @@ void cmNinjaNormalTargetGenerator::WriteDeviceLinkStatement()
     localGen.AddArchitectureFlags(t, &genTarget, cudaLinkLanguage, cfgName);
     vars["ARCH_FLAGS"] = t;
     t = "";
-    localGen.AddLanguageFlags(t, &genTarget, cudaLinkLanguage, cfgName);
+    localGen.AddLanguageFlagsForLinking(t, &genTarget, cudaLinkLanguage,
+                                        cfgName);
     vars["LANGUAGE_COMPILE_FLAGS"] = t;
   }
   if (this->GetGeneratorTarget()->HasSOName(cfgName)) {
@@ -874,7 +875,8 @@ void cmNinjaNormalTargetGenerator::WriteLinkStatement()
     vars["ARCH_FLAGS"] = t;
     t = "";
     t += lwyuFlags;
-    localGen.AddLanguageFlags(t, &genTarget, TargetLinkLanguage, cfgName);
+    localGen.AddLanguageFlagsForLinking(t, &genTarget, TargetLinkLanguage,
+                                        cfgName);
     vars["LANGUAGE_COMPILE_FLAGS"] = t;
   }
   if (this->GetGeneratorTarget()->HasSOName(cfgName)) {