Fix build with clang-cl

qtbase\src\corelib\global\qglobal.cpp(3510,21): error: call to member function 'endsWith' is ambiguous

Change-Id: I2b20077584a33ca5f40efdf397b5913afd6e7fae
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/global/qglobal.cpp

@@ -3507,7 +3507,7 @@ QString qEnvironmentVariable(const char *varName, const QString &defaultValue)
     _wgetenv_s(&requiredSize, reinterpret_cast<wchar_t *>(buffer.data()), requiredSize,
                wname.data());
     // requiredSize includes the terminating null, which we don't want.
-    Q_ASSERT(buffer.endsWith(u'\0'));
+    Q_ASSERT(buffer.endsWith(QChar(u'\0')));
     buffer.chop(1);
     return buffer;
 #else