QLibrary: Suppress GCC 12 warning about dangling pointer access

Introduced in commit d07742f333. Reported
by GCC 12:

qlibrary.cpp:672:9: error: dangling pointer to ‘candidates’ may be used [-Werror=dangling-pointer=]
  672 |         if (isValidSuffix(*it++))
      |         ^~
qlibrary.cpp:634:29: note: ‘candidates’ declared here
  634 |         const QLatin1String candidates[] = {
      |                             ^~~~~~~~~~

This is a false positive report because the lambda does not return a
pointer or iterator. But it's a good update anyway to keep the array
outside the lambda, so it won't be recreated every time.

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104492

Pick-to: 6.3
Change-Id: I74249c52dc02478ba93cfffd16d230abd1bf6166
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

src/corelib/plugin/qlibrary.cpp

@@ -629,7 +629,6 @@ bool QLibrary::isLibrary(const QString &fileName)
     if (completeSuffix.isEmpty())
         return false;
 
-    auto isValidSuffix = [](QStringView s) {
     // if this throws an empty-array error, you need to fix the #ifdef's:
     const QLatin1String candidates[] = {
 # if defined(Q_OS_HPUX)
@@ -652,6 +651,8 @@ bool QLibrary::isLibrary(const QString &fileName)
         QLatin1String("so"),
 # endif
     }; // candidates
+
+    auto isValidSuffix = [&candidates](QStringView s) {
         return std::find(std::begin(candidates), std::end(candidates), s) != std::end(candidates);
     };