title: COMPILE_TIME_ASSERTs all fail referencing dlib as shared library
body: <p>I'm trying to write a JNI wrapper for dlib so that I can obtain face descriptors in Java.
  I've written the jni code to do it, but I can't seem to <code>make</code> it (on MacOS X).
  My JNI doesn't create any compile errors, but a ton of the COMPILE_TIME_ASSERTS fail when <code>make</code>-ing it.</p>
  
  <p>What am I doing wrong and how can I successfully accomplish this?</p>
  
  <p><strong>CmakeLists.txt</strong>:</p>
  
  <pre><code>cmake_minimum_required(VERSION 2.8.12)
  
  project(dlib-jni)
  
  set(CMAKE_CXX_STANDARD 11)
  # add_subdirectory(../dlib dlib_build)
  include_directories(src)
  
  find_package(dlib REQUIRED) #possibly supporting components!
  # include_directories(${OpenCV_INCLUDE_DIRS})
  message(STATUS "Using dlib-${dlib_VERSION}")
  
  find_package(OpenCV 3 REQUIRED)
  include_directories(${OpenCV_INCLUDE_DIRS})
  
  find_package(JNI REQUIRED)
  message (STATUS "JNI_INCLUDE_DIRS=${JNI_INCLUDE_DIRS}")
  message (STATUS "JAVA_INCLUDE_PATH =${JAVA_INCLUDE_PATH}")
  message (STATUS "JNI_LIBRARIES=${JNI_LIBRARIES}")
  message (STATUS "JAVA_JVM_LIBRARY=${JAVA_JVM_LIBRARY}")
  include_directories(${JNI_INCLUDE_DIRS})
  
  add_library(dlib_jni SHARED src/dlib-jni.cpp)
  target_link_libraries(dlib_jni dlib::dlib opencv_core opencv_highgui)
  </code></pre>
  
  <p><strong>cmake Command</strong>:</p>
  
  <pre><code>cmake -DOpenCV_DIR=/usr/local/opt/opencv/share/OpenCV/OpenCVConfig.cmake  ../
  </code></pre>
  
  <p><strong>cmake Output</strong>:</p>
  
  <pre><code>-- The C compiler identification is AppleClang 9.1.0.9020039
  -- The CXX compiler identification is AppleClang 9.1.0.9020039
  -- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc
  -- Check for working C compiler: /Library/Developer/CommandLineTools/usr/bin/cc -- works
  -- Detecting C compiler ABI info
  -- Detecting C compiler ABI info - done
  -- Detecting C compile features
  -- Detecting C compile features - done
  -- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++
  -- Check for working CXX compiler: /Library/Developer/CommandLineTools/usr/bin/c++ -- works
  -- Detecting CXX compiler ABI info
  -- Detecting CXX compiler ABI info - done
  -- Detecting CXX compile features
  -- Detecting CXX compile features - done
  -- Using dlib-19.15.99
  -- Found OpenCV: /usr/local (found suitable version "3.3.1", minimum required is "3") 
  -- Found JNI: /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/libjawt.dylib  
  -- JNI_INCLUDE_DIRS=/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/include;/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/include/darwin;/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/include
  -- JAVA_INCLUDE_PATH =/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/include
  -- JNI_LIBRARIES=/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/libjawt.dylib;/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/server/libjvm.dylib
  -- JAVA_JVM_LIBRARY=/Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home/jre/lib/server/libjvm.dylib
  -- Configuring done
  CMake Warning (dev):
    Policy CMP0042 is not set: MACOSX_RPATH is enabled by default.  Run "cmake
    --help-policy CMP0042" for policy details.  Use the cmake_policy command to
    set the policy and suppress this warning.
  
    MACOSX_RPATH is not specified for the following targets:
  
     dlib_jni
  
  This warning is for project developers.  Use -Wno-dev to suppress it.
  
  -- Generating done
  -- Build files have been written to: /Users/me/gitrepos/dlib-jni/build
  </code></pre>
  
  <p><strong>make command</strong>:</p>
  
  <pre><code>make &amp;&amp; make install
  </code></pre>
  
  <p><strong>First Error (there are many)</strong>:</p>
  
  <pre><code>/usr/local/include/dlib/array2d/../geometry/../image_processing/../image_transforms/image_pyramid.h:940:13: error: static_assert failed "Failed assertion"
              COMPILE_TIME_ASSERT( pixel_traits&lt;in_pixel_type&gt;::has_alpha == false );
  </code></pre>