Meson build for debian obsolete.

jessie-build.ini

########################################################################
# Using up-to-date meson to build for obsolete Debian as a cross-build.
########################################################################
#
# This got me building C & C++ code for Debian Jessie using current
# meson & ninja on Fedora 31.
#
# 1.  Install a Debian Jessie (or whatever) system image into a
#     subdirectory using debootstrap e.g.,
#   sudo debootstrap jessie /opt/debian-8
#
# 2.  Use chroot into this, to install the compilers etc. & the symlinks
#     package.
#
# 3.  Use chroot ... symlinks to relativise links in the system image.
#     E.g., chroot /opt/debian-8 symlinks -cr /usr
#
# Set LD_LIBRARY_PATH appropriately, e.g.,
#
# export LD_LIBRARY_PATH=/usr/lib64:/opt/debian-8/usr/lib/x86_64-linux-gnu
#
# for both meson and ninja.
#
# (I had to put the build library path before the host library path to
# get ninja to run.)
#
# 4.  Do a cross compile using this cross file.  YMMV.
#    meson --cross-file jessie-build.ini jessie
#    ninja -C jessie
#
# I had to manually set pkgconfig here even though the usual one works fine.
# It seems otherwise meson doesn't believe the one in my path is OK for
# the cross-build.  Setting the pkg_config_libdir is essential though.
#
# For C code very likely you could use the host compiler, and target
# libc, for C++ that is unlikely to work, libstdc++ is more complex
# and more coupled to the compiler.
#
[binaries]
c     = '/opt/debian-8/usr/bin/gcc'
cpp   = '/opt/debian-8/usr/bin/g++'
ar    = '/opt/debian-8/usr/bin/gcc-ar'
strip = '/opt/debian-8/usr/bin/strip'
pkgconfig = 'pkg-config'

[properties]
c_args        = ['--sysroot=/opt/debian-8']
c_link_args   = ['--sysroot=/opt/debian-8']
cpp_args      = ['--sysroot=/opt/debian-8']
cpp_link_args = ['--sysroot=/opt/debian-8']

[host_machine]
system = 'linux'
cpu_family = 'x86_64'
cpu = 'x86_64'
endian = 'little'
pkg_config_libdir = '/opt/debian-8/usr/lib/x86_64-linux-gnu/pkgconfig:/opt/debian-8/usr/share/pkgconfig'