Move the constexpr fromArray() check from fromArray() to constExpr()
and there add the protection necessary to work around
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71962, copied from
tst_QByteArrayView.
As a drive-by, add the test for constexpr construction from a char16_t
array, which was missing here (probably because of the GCC bug) while
the corresponding test was already in tst_QByteArrayView.
Amends 107ff4c1d6b5da2cb11c65b2bd9106817f7fdb02(!).
(iow: 6.0, and no, I don't know why it became a problem only now)
Pick-to: 6.7 6.5 6.2
Change-Id: Id9d2a08175709f8bf85b3b192e7aa49783b9e715
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
3f3be9d774