build: add real version numbering

CMakeLists.txt

@@ -16,6 +16,21 @@ set(generic_src_dirs ds init kernel libc sched util vm syscall)
 set(kernel_sources "")
 set(kernel_headers "")
 
+set(version_args --arch ${CMAKE_SYSTEM_PROCESSOR})
+
+if (CMAKE_BUILD_TYPE AND NOT "${CMAKE_BUILD_TYPE}" STREQUAL "Debug")
+	set(version_args ${version_args} "--release")
+endif()
+
+execute_process(
+	COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/tools/magenta.buildid
+		${version_args}
+	OUTPUT_VARIABLE kernel_version
+	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+	OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+message(STATUS "Magenta kernel version: ${kernel_version}")
+
 foreach (dir ${generic_src_dirs})
 	file(GLOB_RECURSE dir_sources ${dir}/*.c)
 	file(GLOB_RECURSE dir_headers ${dir}/*.h)
@@ -52,7 +67,7 @@ add_custom_command(
 	COMMAND ${CMAKE_STRIP} -g $<TARGET_FILE:${kernel_exe_name}>)
 
 target_link_libraries(${kernel_exe_name} -nostdlib -ffreestanding -lgcc)
-target_compile_definitions(${kernel_exe_name} PRIVATE BUILD_ID="0")
+target_compile_definitions(${kernel_exe_name} PRIVATE KERNEL_VERSION="${kernel_version}")
 
 include(arch/${kernel_arch}/config.cmake)
 include(arch/${kernel_arch}/targets.cmake)