Add option to use system cpr

Author: TheAssassin

CMakeLists.txt

@@ -90,6 +90,13 @@ find_package(PkgConfig)
 # now, we use a system provided crypto library for this purpose
 pkg_check_modules(libgcrypt REQUIRED IMPORTED_TARGET libgcrypt)
 
+option(USE_SYSTEM_CPR OFF "Use system-wide installed CPR")
+
+if(USE_SYSTEM_CPR)
+    find_package(cpr REQUIRED)
+    add_library(cpr ALIAS cpr::cpr)
+endif()
+
 # add libraries shipped along with the project
 add_subdirectory(lib)
 

lib/CMakeLists.txt

@@ -10,12 +10,10 @@ add_subdirectory(libzsync)
 
 # external dependencies used as submodules
 
-# using system cURL as it has proper SSL support etc., and reduces the build time
-set(USE_SYSTEM_CURL ON CACHE BOOL "" FORCE)
-# disable CPR tests to save compile time and avoid clashes with own tests
-set(BUILD_CPR_TESTS OFF CACHE BOOL "" FORCE)
-add_subdirectory(cpr)
-set_property(TARGET cpr PROPERTY POSITION_INDEPENDENT_CODE ON)
+if(NOT USE_SYSTEM_CPR)
+    add_subdirectory(cpr)
+    set_property(TARGET cpr PROPERTY POSITION_INDEPENDENT_CODE ON)
+endif()
 
 # it's quite simple dealing with the args library directly from CMake
 add_library(args INTERFACE)

src/CMakeLists.txt

@@ -3,9 +3,6 @@ cmake_minimum_required(VERSION 3.2)
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_POSITION_INDEPENDENT_CODE true)
 
-# fix CPR target
-target_include_directories(cpr PUBLIC ${CPR_INCLUDE_DIRS})
-
 set(zsync2_public_headers
     ${PROJECT_SOURCE_DIR}/include/zsutil.h
     ${PROJECT_SOURCE_DIR}/include/zsclient.h