$NetBSD$

Use pkgsrc openal-soft.

--- src/CMakeLists.txt.orig	2021-02-14 11:47:46.000000000 +0000
+++ src/CMakeLists.txt
@@ -63,6 +63,7 @@ if (BSTONE_USE_STATIC_LINKING)
 	set(BSTONE_SDL2_COMPONENTS "${BSTONE_SDL2_COMPONENTS};static")
 endif ()
 
+find_package(OpenAL 1.7.3 REQUIRED)
 find_package(SDL2W 2.0.4 REQUIRED COMPONENTS ${BSTONE_SDL2_COMPONENTS})
 
 # Threads
@@ -185,6 +186,8 @@ endif ()
 
 target_link_libraries(
 	${PROJECT_NAME}
+	PUBLIC
+		${OPENAL_LIBRARY}
 	PRIVATE
 		SDL2W::SDL2Wmain
 		SDL2W::SDL2W
@@ -216,8 +219,8 @@ target_include_directories(
 	PRIVATE
 		.
 		dosbox
+		${OPENAL_INCLUDE_DIR}
 		lib/glm
-		lib/openal_soft/include/AL
 		lib/stb
 		lib/xbrz
 		sys/win32