cmGlobalNinjaGenerator: Clarify logic for forcing use of response files

Update the WriteBuild method to use a negative command line length limit
to specify that we should force use of response files.

Source/cmGlobalNinjaGenerator.cxx

@@ -230,9 +230,10 @@ void cmGlobalNinjaGenerator::WriteBuild(std::ostream& os,
   std::string assignments = variable_assignments.str();
   const std::string& args = arguments;
   bool useResponseFile = false;
-  if (cmdLineLimit > 0
-      && args.size() + buildstr.size() + assignments.size()
-                                                    > (size_t) cmdLineLimit) {
+  if (cmdLineLimit < 0 ||
+      (cmdLineLimit > 0 &&
+       (args.size() + buildstr.size() + assignments.size())
+       > static_cast<size_t>(cmdLineLimit))) {
     variable_assignments.str(std::string());
     cmGlobalNinjaGenerator::WriteVariable(variable_assignments,
                                           "RSP_FILE", rspfile, "", 1);

Source/cmGlobalNinjaGenerator.h

@@ -94,7 +94,7 @@ public:
                   const cmNinjaDeps& orderOnlyDeps,
                   const cmNinjaVars& variables,
                   const std::string& rspfile = std::string(),
-                  int cmdLineLimit = -1,
+                  int cmdLineLimit = 0,
                   bool* usedResponseFile = 0);
 
   /**

Source/cmNinjaNormalTargetGenerator.cxx

@@ -697,7 +697,7 @@ void cmNinjaNormalTargetGenerator::WriteLinkStatement()
 
   cmGlobalNinjaGenerator& globalGen = *this->GetGlobalGenerator();
 
-  int commandLineLengthLimit = 1;
+  int commandLineLengthLimit = -1;
   if (!this->ForceResponseFile())
     {
     commandLineLengthLimit = calculateCommandLineLengthLimit(