Fix parsing of MSVC's /utf-8 option, take 2

The dash was missing. This commit amends 70e772079.

Task-number: QTBUG-59431
Change-Id: I18f3519a502ca57336cafad574f8738f2e717740
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

qmake/generators/win32/msvc_objectmodel.cpp

@@ -1151,7 +1151,7 @@ bool VCCLCompilerTool::parseOption(const char* option)
     case 'u':
         if (!second)
             UndefineAllPreprocessorDefinitions = _True;
-        else if (second == 't' && third == 'f' && fourth == '8')
+        else if (strcmp(option + 2, "tf-8") == 0)
             AdditionalOptions += option;
         else
             found = false;