Ninja: apply CMAKE_<LANG>_FLAGS_<TYPE> to executable targets (#13069)

Based on a patch by Zaheer Chothia!

Source/cmLocalGenerator.cxx

@@ -1548,13 +1548,10 @@ void cmLocalGenerator::GetTargetFlags(std::string& linkLibs,
            target.GetName());
         return;
         }
-      std::string langVar = "CMAKE_";
-      langVar += linkLanguage;
-      std::string flagsVar = langVar + "_FLAGS";
+      this->AddLanguageFlags(flags, linkLanguage, buildType.c_str());
       std::string sharedFlagsVar = "CMAKE_SHARED_LIBRARY_";
       sharedFlagsVar += linkLanguage;
       sharedFlagsVar += "_FLAGS";
-      flags += this->Makefile->GetSafeDefinition(flagsVar.c_str());
       flags += " ";
       flags += this->Makefile->GetSafeDefinition(sharedFlagsVar.c_str());
       flags += " ";

Source/cmNinjaNormalTargetGenerator.cxx

@@ -193,12 +193,13 @@ cmNinjaNormalTargetGenerator
     vars.LinkFlags = "$LINK_FLAGS";
 
     std::string langFlags;
-    this->GetLocalGenerator()->AddLanguageFlags(langFlags,
-                                                this->TargetLinkLanguage,
-                                                this->GetConfigName());
-    if (targetType != cmTarget::EXECUTABLE)
+    if (targetType != cmTarget::EXECUTABLE) {
+      this->GetLocalGenerator()->AddLanguageFlags(langFlags,
+                                                  this->TargetLinkLanguage,
+                                                  this->GetConfigName());
       langFlags += " $ARCH_FLAGS";
-    vars.LanguageCompileFlags = langFlags.c_str();
+      vars.LanguageCompileFlags = langFlags.c_str();
+    }
 
     // Rule for linking library.
     std::vector<std::string> linkCmds = this->ComputeLinkCmd();