Add CMake support for building the support-lib

Adds the target "djinni" with the options DJINNI_WITH_OBJC,
DJINNI_WITH_JNI and DJINNI_FRAMEWORK.

.gitignore

@@ -34,3 +34,6 @@ intellij-plugin/djinni.jar
 
 # profiling output
 callgrind.out.*
+
+# This is a commonly used folder for CMake output
+/build/

CMakeLists.txt

@@ -0,0 +1,83 @@
+cmake_minimum_required(VERSION 3.5.0 FATAL_ERROR)
+
+project(Djinni)
+
+include(GNUInstallDirs)
+
+add_library(djinni SHARED 
+  "${CMAKE_CURRENT_SOURCE_DIR}/include/djinni/support-lib/djinni_common.hpp"
+  "${CMAKE_CURRENT_SOURCE_DIR}/include/djinni/support-lib/proxy_cache_interface.hpp"
+  "${CMAKE_CURRENT_SOURCE_DIR}/support-lib/proxy_cache_impl.hpp"
+)
+target_include_directories(djinni
+  PUBLIC
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+)
+set_target_properties(djinni PROPERTIES
+  CXX_STANDARD 11
+  CXX_STANDARD_REQUIRED ON
+  CXX_EXTENSIONS OFF
+)
+
+# OBJC support
+option(DJINNI_WITH_OBJC "Include the Objective-C support code in Djinni." OFF)
+if(DJINNI_WITH_OBJC)
+  target_sources(djinni
+    PUBLIC
+    "${CMAKE_CURRENT_SOURCE_DIR}/include/djinni/support-lib/objc/DJICppWrapperCache+Private.h"
+    "${CMAKE_CURRENT_SOURCE_DIR}/include/djinni/support-lib/objc/DJIError.h"
+    "${CMAKE_CURRENT_SOURCE_DIR}/include/djinni/support-lib/objc/DJIMarshal+Private.h"
+    "${CMAKE_CURRENT_SOURCE_DIR}/include/djinni/support-lib/objc/DJIObjcWrapperCache+Private.h"
+    PRIVATE
+    "${CMAKE_CURRENT_SOURCE_DIR}/support-lib/objc/DJIError.mm"
+    "${CMAKE_CURRENT_SOURCE_DIR}/support-lib/objc/DJIProxyCaches.mm"
+)
+target_compile_options(djinni PUBLIC "-fobjc-arc")
+endif()
+
+# JNI SUPPROT
+option(DJINNI_WITH_JNI "Include the JNI support code in Djinni." OFF)
+if(DJINNI_WITH_JNI)
+  target_sources(djinni
+    PUBLIC
+    "${CMAKE_CURRENT_SOURCE_DIR}/include/djinni/support-lib/jni/djinni_support.hpp"
+    "${CMAKE_CURRENT_SOURCE_DIR}/include/djinni/support-lib/jni/Marshal.hpp"
+    PRIVATE
+    "${CMAKE_CURRENT_SOURCE_DIR}/support-lib/jni/djinni_main.cpp"
+    "${CMAKE_CURRENT_SOURCE_DIR}/support-lib/jni/djinni_support.cpp"
+  )
+  # Do not use the host's jni.h on Android as it is provided automatically by the NDK
+  if(NOT ANDROID)
+    find_package(JNI REQUIRED QUIET)
+    target_include_directories(djinni
+      PUBLIC
+      ${JNI_INCLUDE_DIRS}
+    )
+  endif()
+endif()
+
+if(NOT (DJINNI_WITH_OBJC OR DJINNI_WITH_JNI))
+  message(FATAL_ERROR "At least one of DJINNI_WITH_OBJC or DJINNI_WITH_JNI must be enabled.")
+endif()
+
+add_library(dropbox::djinni  ALIAS djinni)
+
+# INSTALLATION
+install(TARGETS djinni
+  LIBRARY   DESTINATION ${CMAKE_INSTALL_LIBDIR}
+  FRAMEWORK DESTINATION ${CMAKE_INSTALL_LIBDIR}
+)
+install(DIRECTORY include/djinni DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+
+# AS APPLE FRAMEWORK
+option(DJINNI_FRAMEWORK "If enabled the Objective-C binary of Djinni is built as djinni.framework otherwise as djinni.dylib on Apple systems." OFF)
+if(APPLE AND DJINNI_FRAMEWORK)
+  set_target_properties(djinni PROPERTIES
+    FRAMEWORK ON
+    MACOSX_FRAMEWORK_IDENTIFIER com.dropbox.djinni
+    XCODE_ATTRIBUTE_INSTALL_PATH "@rpath"
+    OUTPUT_NAME djinni
+  )
+  install(DIRECTORY include/djinni/ DESTINATION ${CMAKE_INSTALL_LIBDIR}/djinni.framework/Header)
+endif()