Add CMake Package Config files during install

- Remove target_include_directories of ${PROJECT_SOURCE_DIR}/include to
  fix error: Target "benchmark" INTERFACE_INCLUDE_DIRECTORIES property
  contains path which is prefixed in the source directory.

cmake/Config.cmake.in

@@ -0,0 +1 @@
+include("${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake")

src/CMakeLists.txt

@@ -27,18 +27,45 @@ if(${CMAKE_SYSTEM_NAME} MATCHES "Windows")
   target_link_libraries(benchmark Shlwapi)
 endif()
 
-# Expose public API
-target_include_directories(benchmark PUBLIC ${PROJECT_SOURCE_DIR}/include)
+set(include_install_dir "include/doctest/")
+set(lib_install_dir "lib/")
+set(bin_install_dir "bin/")
+set(config_install_dir "lib/cmake/${PROJECT_NAME}")
+
+set(generated_dir "${CMAKE_CURRENT_BINARY_DIR}/generated")
+
+set(version_config "${generated_dir}/${PROJECT_NAME}ConfigVersion.cmake")
+set(project_config "${generated_dir}/${PROJECT_NAME}Config.cmake")
+set(targets_export_name "${PROJECT_NAME}Targets")
+
+set(namespace "${PROJECT_NAME}::")
+
+include(CMakePackageConfigHelpers)
+write_basic_package_version_file(
+    "${version_config}" VERSION ${GIT_VERSION} COMPATIBILITY SameMajorVersion
+)
+
+configure_file("${CMAKE_SOURCE_DIR}/cmake/Config.cmake.in" "${project_config}" @ONLY)
 
 # Install target (will install the library to specified CMAKE_INSTALL_PREFIX variable)
 install(
   TARGETS benchmark
-  ARCHIVE DESTINATION lib
-  LIBRARY DESTINATION lib
-  RUNTIME DESTINATION bin
-  COMPONENT library)
+  EXPORT ${targets_export_name}
+  ARCHIVE DESTINATION ${lib_install_dir}
+  LIBRARY DESTINATION ${lib_install_dir}
+  RUNTIME DESTINATION ${bin_install_dir}
+  INCLUDES DESTINATION ${include_install_dir})
 
 install(
   DIRECTORY "${PROJECT_SOURCE_DIR}/include/benchmark"
-  DESTINATION include
+  DESTINATION ${include_install_dir}
   FILES_MATCHING PATTERN "*.*h")
+
+install(
+    FILES "${project_config}" "${version_config}"
+    DESTINATION "${config_install_dir}")
+
+install(
+    EXPORT "${targets_export_name}"
+    NAMESPACE "${namespace}"
+    DESTINATION "${config_install_dir}")