ENH: Fix argument parsing on UNIX with spaces

Source/cmSystemTools.cxx

@@ -349,10 +349,22 @@ bool cmSystemTools::RunSingleCommand(
       {
       // Parse an unquoted argument.
       while(*c && *c != ' ' && *c != '\t')
+        {
+        if(*c == '\\')
+          {
+          ++c;
+          if(*c)
             {
             arg.append(1, *c);
             ++c;
             }
+          }
+        else
+          {
+          arg.append(1, *c);
+          ++c;
+          }
+        }
       args.push_back(arg);
       }
     }