Move the EscapeJSON method to a sharable location.

Source/cmGlobalGenerator.cxx

@@ -2474,3 +2474,16 @@ void cmGlobalGenerator::WriteSummary(cmTarget* target)
     cmSystemTools::RemoveFile(file.c_str());
     }
 }
+
+//----------------------------------------------------------------------------
+// static
+std::string cmGlobalGenerator::EscapeJSON(const std::string& s) {
+  std::string result;
+  for (std::string::size_type i = 0; i < s.size(); ++i) {
+    if (s[i] == '"' || s[i] == '\\') {
+      result += '\\';
+    }
+    result += s[i];
+  }
+  return result;
+}