cmMakefile: Simplify custom target 'force' output name generation

Remove unnecessary check of policy CMP0049.  The policy can never
trigger on our internally-generated name because it has no variable
references.

The rename in commit 0ed5ce4cd8 (cmTarget: Rename AddSource method for
backward compatibility., 2014-03-17, v3.1.0-rc1~688^2~17) made it look
like this code path depended on CMP0049.  Then commit 0e1faa28cb
(cmMakefile: Separate custom command setup from actual creation,
2019-09-14, v3.16.0-rc1~85^2) and commit ea1bed34b2 (cmMakefile: Extract
utilities used for creation of custom commands, 2019-09-21,
v3.16.0-rc1~52^2~1) built additional infrastructure to thread that
dependence through the call stack.  Remove it all.

Source/cmCustomCommandTypes.h

@@ -27,10 +27,3 @@ enum class cmObjectLibraryCommands
   Reject,
   Accept
 };
-
-/** Utility target output source file name.  */
-struct cmUtilityOutput
-{
-  std::string Name;
-  std::string NameCMP0049;
-};

Source/cmLocalGenerator.cxx

@@ -4115,7 +4115,7 @@ void AppendCustomCommandToOutput(cmLocalGenerator& lg,
 
 void AddUtilityCommand(cmLocalGenerator& lg, const cmListFileBacktrace& lfbt,
                        cmCommandOrigin origin, cmTarget* target,
-                       const cmUtilityOutput& force, const char* workingDir,
+                       std::string const& force, const char* workingDir,
                        const std::vector<std::string>& byproducts,
                        const std::vector<std::string>& depends,
                        const cmCustomCommandLines& commandLines,
@@ -4131,7 +4131,7 @@ void AddUtilityCommand(cmLocalGenerator& lg, const cmListFileBacktrace& lfbt,
   std::string no_main_dependency;
   cmImplicitDependsList no_implicit_depends;
   cmSourceFile* rule = AddCustomCommand(
-    lg, lfbt, origin, { force.Name }, byproducts, depends, no_main_dependency,
+    lg, lfbt, origin, { force }, byproducts, depends, no_main_dependency,
     no_implicit_depends, commandLines, comment, workingDir,
     /*replace=*/false, escapeOldStyle, uses_terminal, command_expand_lists,
     /*depfile=*/"", job_pool, stdPipesUTF8);
@@ -4139,9 +4139,7 @@ void AddUtilityCommand(cmLocalGenerator& lg, const cmListFileBacktrace& lfbt,
     lg.AddTargetByproducts(target, byproducts, lfbt, origin);
   }
 
-  if (!force.NameCMP0049.empty()) {
+  target->AddSource(force);
-    target->AddSource(force.NameCMP0049);
-  }
 }
 
 std::vector<std::string> ComputeISPCObjectSuffixes(cmGeneratorTarget* target)

Source/cmLocalGenerator.h

@@ -684,7 +684,7 @@ void AppendCustomCommandToOutput(cmLocalGenerator& lg,
 
 void AddUtilityCommand(cmLocalGenerator& lg, const cmListFileBacktrace& lfbt,
                        cmCommandOrigin origin, cmTarget* target,
-                       const cmUtilityOutput& force, const char* workingDir,
+                       std::string const& force, const char* workingDir,
                        const std::vector<std::string>& byproducts,
                        const std::vector<std::string>& depends,
                        const cmCustomCommandLines& commandLines,

Source/cmMakefile.cxx

@@ -1257,25 +1257,18 @@ void cmMakefile::AppendCustomCommandToOutput(
   }
 }
 
-cmUtilityOutput cmMakefile::GetUtilityOutput(cmTarget* target)
+std::string cmMakefile::GetUtilityOutput(cmTarget* target)
 {
   std::string force = cmStrCat(this->GetCurrentBinaryDirectory(),
                                "/CMakeFiles/", target->GetName());
-  std::string forceCMP0049 = target->GetSourceCMP0049(force);
+  // The output is not actually created so mark it symbolic.
-  {
+  if (cmSourceFile* sf = this->GetOrCreateSource(
-    cmSourceFile* sf = nullptr;
+        force, false, cmSourceFileLocationKind::Known)) {
-    if (!forceCMP0049.empty()) {
+    sf->SetProperty("SYMBOLIC", "1");
-      sf = this->GetOrCreateSource(forceCMP0049, false,
+  } else {
-                                   cmSourceFileLocationKind::Known);
+    cmSystemTools::Error("Could not get source file entry for " + force);
-    }
-    // The output is not actually created so mark it symbolic.
-    if (sf) {
-      sf->SetProperty("SYMBOLIC", "1");
-    } else {
-      cmSystemTools::Error("Could not get source file entry for " + force);
-    }
   }
-  return { std::move(force), std::move(forceCMP0049) };
+  return force;
 }
 
 cmTarget* cmMakefile::AddUtilityCommand(
@@ -1295,8 +1288,8 @@ cmTarget* cmMakefile::AddUtilityCommand(
   }
 
   // Get the output name of the utility target and mark it generated.
-  cmUtilityOutput force = this->GetUtilityOutput(target);
+  std::string force = this->GetUtilityOutput(target);
-  this->GetOrCreateGeneratedSource(force.Name);
+  this->GetOrCreateGeneratedSource(force);
 
   // Always create the byproduct sources and mark them generated.
   this->CreateGeneratedOutputs(byproducts);

Source/cmMakefile.h

@@ -243,9 +243,9 @@ public:
                           bool excludeFromAll = false);
 
   /**
-   * Return the utility target output source file name and the CMP0049 name.
+   * Return the utility target output source file name.
    */
-  cmUtilityOutput GetUtilityOutput(cmTarget* target);
+  std::string GetUtilityOutput(cmTarget* target);
 
   /**
    * Dispatch adding a utility to the build.  A utility target is a command