ProjectExplorer: Replace the fromMap error return value for toolchains

... by some out-of-band mechanism, keeping previous functionality.

The driving reason is to get the same fromMap signature as in the
AspectContainer base.

Change-Id: Ife7fbf4d0e0f78d88729021eb5220ec4a8ddb2ec
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/android/androidtoolchain.cpp

@@ -101,11 +101,13 @@ void AndroidToolChain::addToEnvironment(Environment &env) const
     env.set(QLatin1String("ANDROID_SDK_ROOT"), config.sdkLocation().toUserOutput());
 }
 
-bool AndroidToolChain::fromMap(const QVariantMap &data)
+void AndroidToolChain::fromMap(const QVariantMap &data)
 {
-    if (!ClangToolChain::fromMap(data))
-        return false;
-    return isValid();
+    ClangToolChain::fromMap(data);
+    if (hasError())
+        return;
+    if (!isValid())
+        reportError();
 }
 
 QStringList AndroidToolChain::suggestedMkspecList() const