fix qmake warning about unknown /Zc:strictStrings option

Make /Zc:strictStrings known to qmake's MSVC compiler option parser.

Change-Id: I5a4494096fc1d67c96c6de52bb0f1e94eff46136
(cherry picked from commit qtbase/55f88e6e310ceb99bef31ed8d884deaa55c78d91)
Reviewed-by: Oswald Buddenhagen <[email protected]>
Reviewed-by: Joerg Bornemann <[email protected]>

Author: jobor

qmake/generators/win32/msvc_objectmodel.cpp

@@ -909,6 +909,8 @@ bool VCCLCompilerTool::parseOption(const char* option)
                     ForceConformanceInForLoopScope = ((*c) == '-' ? _False : _True);
                 else if(fourth == 'w')
                     TreatWChar_tAsBuiltInType = ((*c) == '-' ? _False : _True);
+                else if (config->CompilerVersion >= NET2013 && strncmp(option + 4, "strictStrings", 13) == 0)
+                    AdditionalOptions += option;
                 else
                     found = false;
             } else {