Starting with Solaris 11.4 (which is now the required minimal version), Solaris does
support __cxa_atexit. This patch reflects that.
One might consider removing the affected tests altogether instead of inverting them,
as is done on other targets.
Besides, this lets two ASan tests PASS:
AddressSanitizer-i386-sunos :: TestCases/init-order-atexit.cc AddressSanitizer-i386-sunos-dynamic :: TestCases/init-order-atexit.cc
Tested on x86_64-pc-solaris2.11 and sparcv9-sun-solaris2.11. Ok for trunk?