see #95 (comment)

Author: Pfeifenjoy

CMakeLists.txt

@@ -13,7 +13,7 @@ if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
 endif()
 
 add_library(json11 json11.cpp)
-target_include_directories(json11 PUBLIC ${CMAKE_SOURCE_DIR})
+target_include_directories(json11 PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 target_compile_options(json11
  PRIVATE -fPIC -fno-rtti -fno-exceptions -Wall -Wextra -Werror)
 configure_file("json11.pc.in" "json11.pc" @ONLY)