QProcess/Unix: also ban vfork() under TSan

Complements 94ec17436cbdab52ed85e15ea197b538541b14ca for the ASan logic
(52ed6af5277100ed5b9a4f4231b94013ce539a2c for the code change).

Fixes: QTBUG-117533
Pick-to: 6.6
Change-Id: I09c3950e719e4b259bc7fffd1793d59dbdbfe82a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Jonas Karlsson <jonas.karlsson@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/corelib/io/qprocess_unix.cpp

@@ -622,6 +622,10 @@ inline bool globalUsingVfork() noexcept
     // ASan writes to global memory, so we mustn't use vfork().
     return false;
 #endif
+#if defined(__SANITIZE_THREAD__) || __has_feature(thread_sanitizer)
+    // Ditto, apparently
+    return false;
+#endif
 #if defined(Q_OS_LINUX) && !QT_CONFIG(forkfd_pidfd)
     // some broken environments are known to have problems with the new Linux
     // API, so we have a way for users to opt-out during configure time (see