iOS: Fixes false warnings about iOS kit and Qt version

iOS Qt version complains about missing compilers and the corresponding kit
complains about unsupported device

Task-number: QTCREATORBUG-16472
Change-Id: Ie2185e33ec5043de0230a325b48b21dc1a25109e
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/projectexplorer/toolchain.cpp

@@ -135,6 +135,11 @@ Core::Id ToolChain::typeId() const
     return d->m_typeId;
 }
 
+QList<Abi> ToolChain::supportedAbis() const
+{
+    return { targetAbi() };
+}
+
 bool ToolChain::canClone() const
 {
     return true;