Fix include paths with subfolder

When an autotools project is using SUBDIRS it starts a new parser. The
new parser object was not propagating includes/defines/flags to the main
parser object, and thus the code model did miss those.
This commit fixes that.

Task-number: QTCREATORBUG-21618
Change-Id: I19ed4dd3820257378e888f3c4935ebd30e958828
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/autotoolsprojectmanager/makefileparser.cpp

@@ -291,11 +291,26 @@ void MakefileParser::parseSubDirs()
         foreach (const QString& source, parser.sources())
             m_sources.append(subDir + slash + source);
 
+        // Append the include paths of the sub directory
+        m_includePaths.append(parser.includePaths());
+
+        // Append the flags of the sub directory
+        m_cflags.append(parser.cflags());
+        m_cxxflags.append(parser.cxxflags());
+
+        // Append the macros of the sub directory
+        foreach (const auto& m, parser.macros())
+        {
+            if (!m_macros.contains(m))
+                m_macros.append(m);
+        }
+
+    }
+
     // Duplicates might be possible in combination with several
     // "..._SUBDIRS" targets
     m_makefiles.removeDuplicates();
     m_sources.removeDuplicates();
-    }
 
     if (subDirs.isEmpty())
         m_success = false;