Abi: Only have one "generic" flavor

Replace GenericLinuxFlavor, GenericUnixFlavor, GenericDarwinFlavor,
GenericQnxFlavor and GenericBareMetalFlavor with GenericFlavor. They
can all be distinguished from each other by the OS property, so having
separate enum values for all of them is not necessary.

Remove a unit test that made sure that each flavor (with exceptions)
is only listed for one OS, which no longer is the case now.

Change-Id: I88dad5d37eaa4c288568e40b95337a39b78a8352
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/ios/iosqtversion.cpp

@@ -85,7 +85,7 @@ QList<Abi> IosQtVersion::detectQtAbis() const
     for (int i = 0; i < abis.count(); ++i) {
         abis[i] = Abi(abis.at(i).architecture(),
                       abis.at(i).os(),
-                      Abi::GenericDarwinFlavor,
+                      Abi::GenericFlavor,
                       abis.at(i).binaryFormat(),
                       abis.at(i).wordWidth());
     }