title: Autotools build fails due to subdir-objects option in AM_INIT_AUTOMAKE
body: <p>I'm currently working on a C++ project which relies on recursive automake for building. 
  I want to build a shared library and the <code>Makefile.am</code> in the <code>src</code> directory of the library looks like</p>
  
  <pre><code># ...
  
  # Library name
  lib_LTLIBRARIES = libadapter-@MY_API_VERSION@.la
  
  # Sources
  libadapter_@MY_API_VERSION@_la_SOURCES = \
      $(top_builddir)/src/sourceA.cpp \
      $(top_builddir)/src/sourceB.cpp
  
  # ...
  </code></pre>
  
  <p>Since version 1.14, automake issues a warning when the <code>subdir-objects</code> option is not specified in <code>AM_INIT_AUTOMAKE</code> in <code>configure.ac</code>. However, adding the <code>subdir-objects</code> option seems to break the build process with <code>make</code> complaining about missing <code>.Plo</code> files. I already searched the web for people experiencing similar problems but did not find any sensible hint on how to resolve the issue without changing the project to a non-recursive one. Any help is greatly appreciated.</p>
  
  <p><strong>EDIT:</strong>
  Diving more deeply into the problem, I noted that <code>./configure</code> creates a directory literally named <code>$(top_builddir)</code> below the current source directory of the library, which contains all the required <code>.Plo</code> files for building the library. In the <code>Makefile</code>, however, I found that the <code>.Plo</code> equivalents of my library sources (<code>sourceA.cpp</code> and <code>sourceB.cpp</code> in the example) are prefixed by <code>include $(top_builddir)/src/$(DEPDIR)/</code> and <code>$(top_builddir)</code> is a variable defined as a <em>relative</em> path (namely, <code>../../../src/.deps/</code>). Now it becomes clear why <code>make</code> can't find the <code>.Plo</code> files because it searches the wrong directory. This looks like a possible duplicate of bug <a href="https://lists.gnu.org/archive/html/bug-automake/2014-01/msg00005.html" rel="noreferrer">#16375</a>. Any workarounds?</p>
  
  <p><strong>EDIT 2:</strong>
  Digging further in the web revealed two more threads which address the issue: <a href="http://mytestbed.net/issues/1327" rel="noreferrer">#1327</a> and <a href="http://lists.gnu.org/archive/html/bug-automake/2004-01/msg00044.html" rel="noreferrer">automake-bug</a>. A known workaround seems to be passing the <code>--disable-dependency-tracking</code> option to <code>./configure</code>. At least for me it works.</p>