Fix public usage requirements on CMake targets (#462)

This adds the include directory to the public includes for both the
static and shared targets. It is necessary to do it for both the build
and install interfaces, because the build interface will be used if the
project is added as a submodule, but the install interface will be used
if the project was added using a config.

Fixes #460.

Co-authored-by: Jung-Sang Ahn <[email protected]>

CMakeLists.txt

@@ -278,6 +278,20 @@ set_target_properties(static_lib PROPERTIES OUTPUT_NAME ${LIBRARY_NAME} CLEAN_DI
 add_library(shared_lib SHARED ${STATIC_LIB_SRC})
 add_library(NuRaft::shared_lib ALIAS shared_lib)
 set_target_properties(shared_lib PROPERTIES OUTPUT_NAME ${LIBRARY_NAME} CLEAN_DIRECT_OUTPUT 1)
+
+# Include directories are necessary for dependents to use the targets.
+target_include_directories(static_lib
+    PUBLIC
+        $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+        $<INSTALL_INTERFACE:${CMAKE_INSTALL_PREFIX}/include>
+)
+
+target_include_directories(static_lib
+    PUBLIC
+        $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+        $<INSTALL_INTERFACE:${CMAKE_INSTALL_PREFIX}/include>
+)
+
 if (APPLE)
     target_link_libraries(shared_lib ${LIBRARIES})
 endif ()