Update JSON build dependency

I think I finally worked out the issues w/ linking against the
nlohmann JSON library.  I have updated the build and the various
CI scripts.

.ci/install.sh

@@ -6,4 +6,6 @@ if [ $TRAVIS_OS_NAME == osx ]; then
     brew update || true
     brew upgrade boost || true
     brew install libsodium clang-format
+    brew tap nlohmann/json
+    brew install nlohmann_json
 fi

.ci/script.sh

@@ -32,6 +32,7 @@ if [ $TRAVIS_OS_NAME == osx ]; then
     cmake -Hdeps -B.deps -DCMAKE_BUILD_TYPE=Release \
         -DUSE_BUNDLED_BOOST=OFF \
         -DUSE_BUNDLED_GTEST=OFF
+        -DUSE_BUNDLED_JSON=OFF
     cmake --build .deps
 
     # Build the library.

CMakeLists.txt

@@ -170,7 +170,8 @@ target_link_libraries(matrix_client
                       OpenSSL::Crypto
                       OpenSSL::SSL
                       Olm::Olm
-                      ZLIB::ZLIB)
+                      ZLIB::ZLIB
+                      nlohmann_json::nlohmann_json)
 
 if(NOT MSVC AND NOT APPLE)
   target_link_libraries(matrix_client PUBLIC Threads::Threads)

Makefile

@@ -10,7 +10,7 @@ help: ## This help message
 	@# Change the digit following by an 's' to adjust the width of the help text
 
 third-party: ## Build & install third party dependencies
-	@cmake -GNinja -H${DEPS_SOURCE_DIR} -B${DEPS_BUILD_DIR} -DCMAKE_BUILD_TYPE=Release -DUSE_BUNDLED_BOOST=OFF
+	@cmake -GNinja -H${DEPS_SOURCE_DIR} -B${DEPS_BUILD_DIR} -DCMAKE_BUILD_TYPE=Release -DUSE_BUNDLED_BOOST=OFF -DUSE_BUNDLED_JSON=OFF
 	@cmake --build ${DEPS_BUILD_DIR}
 
 debug: ## Create a debug build

appveyor.yml

@@ -38,6 +38,7 @@ build_script:
         -DUSE_BUNDLED_BOOST=OFF
         -DUSE_BUNDLED_SPDLOG=OFF
         -DUSE_BUNDLED_GTEST=OFF
+        -DUSE_BUNDLED_JSON=OFF
     - cmake --build .deps --config Release
 
     - cmake -G "Visual Studio 15 2017 Win64" -H. -Bbuild

deps/CMakeLists.txt

@@ -26,6 +26,7 @@ option(USE_BUNDLED_SPDLOG "Use the bundled version of spdlog." ${USE_BUNDLED})
 option(USE_BUNDLED_OLM "Use the bundled version of libolm." ${USE_BUNDLED})
 option(USE_BUNDLED_GTEST "Use the bundled version of Google Test."
        ${USE_BUNDLED})
+option(USE_BUNDLED_JSON "Use the bundled version of nlohmann json." ${USE_BUNDLED})
 
 option(USE_EXISTING_SRC_DIR
        "Skip download of deps sources in case of existing source directory."
@@ -53,13 +54,14 @@ set(SPDLOG_URL https://github.com/gabime/spdlog/archive/v1.1.0.tar.gz)
 set(SPDLOG_HASH
     3dbcbfd8c07e25f5e0d662b194d3a7772ef214358c49ada23c044c4747ce8b19)
 
-set(JSON_HEADER_URL
-    https://github.com/nlohmann/json/releases/download/v3.2.0/json.hpp)
-set(JSON_HEADER_HASH
-    ce6b5610a051ec6795fa11c33854abebb086f0fd67c311f5921c3c07f9531b44)
+set(JSON_URL
+    https://github.com/nlohmann/json.git)
+set(JSON_TAG
+    v3.2.0)
 
-file(DOWNLOAD ${JSON_HEADER_URL} ${DEPS_INSTALL_DIR}/nlohmann/include/json.hpp
-     EXPECTED_HASH SHA256=${JSON_HEADER_HASH})
+if(USE_BUNDLED_JSON)
+  include(Json)
+endif()
 
 if(USE_BUNDLED_BOOST)
   include(Boost)

deps/cmake/Json.cmake

+ExternalProject_Add(
+  Json
+
+  GIT_REPOSITORY ${JSON_URL}
+  GIT_TAG ${JSON_TAG}
+
+  BUILD_IN_SOURCE 1
+  SOURCE_DIR ${DEPS_BUILD_DIR}/json
+
+  CONFIGURE_COMMAND ${CMAKE_COMMAND}
+        -DJSON_BuildTests=OFF
+        -DCMAKE_INSTALL_PREFIX=${DEPS_INSTALL_DIR}
+        -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}
+
+  BUILD_COMMAND ${CMAKE_COMMAND} --build ${DEPS_BUILD_DIR}/json 
+  INSTALL_COMMAND make install
+)
+
+list(APPEND THIRD_PARTY_DEPS Json)