QLocale: Fix test on MinGW 8.1.0 32 bit

The call of _control87 would crash because of the previous test.

Change-Id: I254efe9c2e9892a473a02663e5ff7016791d5d6d
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@qt.io>

tests/auto/corelib/text/qlocale/tst_qlocale.cpp

@@ -1395,6 +1395,7 @@ void tst_QLocale::fpExceptions()
     // check that double-to-string conversion doesn't throw floating point exceptions when they are
     // enabled
 #ifdef Q_OS_WIN
+    _clear87();
     unsigned int oldbits = _control87(0, 0);
     _control87( 0 | _EM_INEXACT, _MCW_EM );
 #endif