Convert macros from plain QByteArray to a vector of structs

The old code model expected the macros as C++ formatted text
("#define Foo 42) but newer targets like the Clang codemodel expect key
value arguments like "-DFoo=42". So instead of parsing the text again and
again we use an abstract data description.

Task-number: QTCREATORBUG-17915
Change-Id: I0179fd13c48a581e91ee79bba9d42d501c26f19f
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/nim/project/nimtoolchain.cpp

@@ -82,9 +82,9 @@ ToolChain::PredefinedMacrosRunner NimToolChain::createPredefinedMacrosRunner() c
     return ToolChain::PredefinedMacrosRunner();
 }
 
-QByteArray NimToolChain::predefinedMacros(const QStringList &) const
+Macros NimToolChain::predefinedMacros(const QStringList &) const
 {
-    return QByteArray();
+    return Macros();
 }
 
 ToolChain::CompilerFlags NimToolChain::compilerFlags(const QStringList &) const