This package contain Kbuild, the Linux kernel build system.
This package contain a simple copy of Kbuild with minor changes to be used out of the linux kernel tree.

I) Installation
install.py -o <install folder>
or
install.py to install Kbuild in /usr/share/Kbuild/

II) Update Kbuild
./install -i <kernel folder> -o ./
This command will copy Kbuild from kernel tree to this package.

III) Use Kbuild
Your Makefile will never include a file from Kbuild but install but exports
some environment variables and call Makefile.app

1) Environment variables
KBUILD_SRC: set the source directory for out of tree build
KCONFIG_CONFIG: the name of config file to use (default .config)
KBUILD_CFLAGS: CFLAGS to use to build the target
KBUILD_LDFLAGS: LDFLAGS to use to build the target
CONFIG_TARGETS: List of defconfigs
*APP_SRC: list of folders containing the sources
*KBUILD_IMAGE: Name of binary to produce

*: mandatory

2) targets
all: build the image
menuconfig: run the configuration tool (require kconfig-frontend)
clean: remove object file
distclean: clean + configuration files
mrproper: remove any generated file
help: display available targets

3) Example of Makefile:
KBUILD_IMAGE := helloworld
APP_SRC = src/
export KBUILD_IMAGE APP_SRC
all:
	$(Q)$(MAKE) -f /usr/share/Kbuild/Makefile.app all
menuconfig:
	$(Q)$(MAKE) -f /usr/share/Kbuild/Makefile.app menuconfig
clean:
	$(Q)$(MAKE) -f /usr/share/Kbuild/Makefile.app clean
distclean:
	$(Q)$(MAKE) -f /usr/share/Kbuild/Makefile.app distclean

For sub directories Makefiles, please refer to https://www.kernel.org/doc/Documentation/kbuild/makefiles.txt


IV) Know issues
CFLAGS_$@, AFLAGS_$@, LDFLAGS_$@ and OBJCOPYFLAGS_$@ currently does not work.