readme-buildroot-howto

download buildroot-2020.08.2.tar.gz and extract it. the version contains python 3.8.6. 
install host packages listed in the buildroot user manual.


gather information from the target: cpu a53, kernel 4.6, gcc 6.3, aarch64 little endian


configure buildroot for a base build:

  run 
    make menuconfig

  select in menuconfig
    target options
        aarch64 little endian
        cortex-a53
    toolchain
        external toolchain
        custom toolchain
        pre-installed toolchain
        /opt/hm-linux/x86-arm/aarch64-hm-linux toolchain path
        $(ARCH)-hm-linux toolchain prefix
        gcc version 6.x
        kernel header series 4.6.x
        C library glibc/eglibc
        toolchain has C++ support

  run 
    make


configure buildroot to include python3 and build:

  run make menuconfig to select 
    target package
        interpreted language
            python3

  make a time stamp in file system
    touch stamp1

  run
    make V=1 > log-build-screen 2>&1 

  inspect the log file and dl directory, new packages are downloaded and built
    $ find dl -newer stamp1
    dl/expat/expat-2.2.9.tar.xz
    dl/python3/Python-3.8.6.tar.xz
    dl/pkgconf/pkgconf-1.6.1.tar.xz
    dl/libffi/libffi-3.3.tar.gz
    dl/libzlib/zlib-1.2.11.tar.xz

  get a list of new files in target directory
    $ (cd output/target && find ./ -newer ../../stamp1)

  edit the list to exclude files that should not be copied.
  exclude the usr/lib/python3.8/ directory from the list. 
  exclude files existing on the target. 
  verify new files in /lib/ are on target under /lib64/ and of the same version each.
  the final list is: 
    Link: ./usr/lib/libffi.so
    File: ./usr/lib/libpython3.so
    File: ./usr/lib/libpython3.8.so.1.0
    File: ./usr/lib/libffi.so.7.1.0
    Link: ./usr/lib/libffi.so.7
    Link: ./usr/lib/libpython3.8.so
    Link: ./usr/bin/python3
    File: ./usr/bin/python3.8
    Link: ./usr/bin/python

  copy these files and links to the target. copy usr/lib/python3.8/ to the target. 


configure to include python-pip package
  stamp and build
  inspect downloaded packages
    $ find dl -newer stamp2
    dl/libopenssl/openssl-1.1.1g.tar.gz
    dl/python-setuptools/setuptools-44.0.0.zip
    dl/python-pip/pip-20.0.2.tar.gz

  find new files under output/target and copy these files: 
    ./usr/lib/libz.so.1.2.11
    ./usr/lib/libssl.so
    ./usr/lib/libssl.so.1.1
    ./usr/lib/libcrypto.so.1.1
    ./usr/lib/libz.so.1
    ./usr/lib/libz.so
    ./usr/lib/libexpat.so.1
    ./usr/lib/libcrypto.so
    ./usr/lib/libpython3.so
    ./usr/lib/libpython3.8.so.1.0
    ./usr/lib/libffi.so.7.1.0
    ./usr/lib/libexpat.so
    ./usr/lib/libexpat.so.1.6.11
    ./usr/bin/easy_install-3.8
    ./usr/bin/xmlwf
    ./usr/bin/pip3.8
    ./usr/bin/python3.8
    ./usr/bin/pip
    ./usr/bin/pip3
    ./usr/bin/easy_install


configure to include zlib support in legacy packages
  it looks no artifacts difference. so take it out. 


need to rebuild host-python3 packages too to get the zlib and xml compiled. 
  zlib and xml are enabled by pip. but the frozenimportlib is built by host-python.
  find all the *python* packages under output/build/ and do a -dirclean on them:

    make host-python3-dirclean
    make python3-dirclean

  rebuild:
    make