ProjectExplorer: (Re-)start using strings for mkspecs

Even if this is part of a directory name it is naturally closer to a
"string" id than a file path.

Change-Id: If66f930526744379ce86e2b18bd9eac7fabfe773
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/android/androidtoolchain.cpp

@@ -123,10 +123,9 @@ bool AndroidToolChain::fromMap(const QVariantMap &data)
     return isValid();
 }
 
-FileNameList AndroidToolChain::suggestedMkspecList() const
+QStringList AndroidToolChain::suggestedMkspecList() const
 {
-    return FileNameList() << FileName::fromLatin1("android-g++")
-                          << FileName::fromLatin1("android-clang");
+    return {"android-g++", "android-clang"};
 }
 
 FileName AndroidToolChain::makeCommand(const Environment &env) const