x86_64: remove kernel image post-build ELF32 patch

this patch must now be done by the wider OS build system, to avoid
interference with any bootloaders that don't support this kind of
patching (e.g GRUB i386-pc)

arch/x86_64/config.cmake

@@ -2,9 +2,3 @@ target_compile_options(${kernel_exe_name} PRIVATE
 	-z max-page-size=0x1000 -m64 -mcmodel=large -mno-red-zone -mno-mmx
 	-mno-sse -mno-sse2 -D_64BIT -DBYTE_ORDER=1234)
 target_link_libraries(${kernel_exe_name} "-z max-page-size=0x1000" "-T ${CMAKE_CURRENT_SOURCE_DIR}/arch/x86_64/layout.ld")
-
-add_custom_command(TARGET ${kernel_exe_name} POST_BUILD
-	COMMAND ${BUILD_TOOLS_DIR}/e64patch $<TARGET_FILE:${kernel_exe_name}>
-	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
-	COMMENT "Patching kernel elf64 image"
-)