title: Why doesn't Bazel find my include file despite using copts to add an extra include directory?
body: <p>I've modified the stage3 cpp bazelbuild example to use an extra include paths via <code>copts</code></p>
  
  <p><a href="https://github.com/mnieber/examples/commit/a8b784ddf5698563a31401b9ac3531636b3536ef" rel="nofollow noreferrer">https://github.com/mnieber/examples/commit/a8b784ddf5698563a31401b9ac3531636b3536ef</a></p>
  
  <p>However, this produces a compiler error (note though that <code>-Ilib/foo</code> is used as an option for <code>gcc</code>):</p>
  
  <pre><code>bazel build --verbose_failures //main:hello-world
  INFO: Analysed target //main:hello-world (1 packages loaded).
  INFO: Found 1 target...
  ERROR: /home/maarten/sources/examples/cpp-tutorial/stage3/lib/BUILD:1:1: C++ compilation of rule '//lib:hello-time' failed (Exit 1): gcc failed: error executing command 
    (cd /home/maarten/.cache/bazel/_bazel_maarten/62d72ea3bd73864cf884808e7d850715/execroot/__main__ &amp;&amp; \
    exec env - \
      LD_LIBRARY_PATH=/usr/local/lib \
      PATH=/home/maarten/projects/xmlparser/dodo_commands/env/bin:/home/maarten/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/home/dodo/env/bin:/home/maarten/.dodo_commands/bin \
      PWD=/proc/self/cwd \
    /usr/bin/gcc -U_FORTIFY_SOURCE -fstack-protector -Wall -B/usr/bin -B/usr/bin -Wunused-but-set-parameter -Wno-free-nonheap-object -fno-omit-frame-pointer '-std=c++0x' -MD -MF bazel-out/k8-fastbuild/bin/lib/_objs/hello-time/hello-time.pic.d '-frandom-seed=bazel-out/k8-fastbuild/bin/lib/_objs/hello-time/hello-time.pic.o' -fPIC -iquote . -iquote bazel-out/k8-fastbuild/genfiles -iquote bazel-out/k8-fastbuild/bin -iquote external/bazel_tools -iquote bazel-out/k8-fastbuild/genfiles/external/bazel_tools -iquote bazel-out/k8-fastbuild/bin/external/bazel_tools -Ilib/foo -fno-canonical-system-headers -Wno-builtin-macro-redefined '-D__DATE__="redacted"' '-D__TIMESTAMP__="redacted"' '-D__TIME__="redacted"' -c lib/hello-time.cc -o bazel-out/k8-fastbuild/bin/lib/_objs/hello-time/hello-time.pic.o)
  
  Use --sandbox_debug to see verbose messages from the sandbox
  lib/hello-time.cc:2:21: fatal error: bar/baz.h: No such file or directory
  compilation terminated.
  Target //main:hello-world failed to build
  </code></pre>
  
  <p>Can someone explain why <code>bar/baz.h</code> is not found?</p>