package/pkg-generic.mk: rework pkg_size logic with the "installed" step

package/pkg-generic.mk: rework pkg_size logic with the "installed" step

This commits reworks the pkg_size logic to no longer use the
GLOBAL_INSTRUMENTATION_HOOKS mechanism, but instead be directly
implemented within the configure step and install step.

The problem with the current implementation in the
GLOBAL_INSTRUMENTATION_HOOKS is that we only capture what is installed
in $(HOST_DIR) during the "host installation step", what is installed
in $(TARGET_DIR) during the "target installation step" and what is
installed in "$(STAGING_DIR)" during the staging installation step.

While this seems reasonable in principle, it is in fact not completely
true. For example, "toolchain", which is a target package, installs
tons of files in $(HOST_DIR). "qt5base", which is also a target
package, also installs things in $(HOST_DIR). Same with the "syslinux"
package.

The idea behind this patch is pretty simple:

 - At the beginning of the configure step, right after the per-package
   directories have been populated (if BR2_PER_PACKAGE_DIRECTORIES=y),
   we capture the state of the HOST_DIR, TARGET_DIR and STAGING_DIR.

 - At the end of all install steps (which is possible thanks to the
   newly introduced "install" step), we capture again the state of
   HOST_DIR, TARGET_DIR and STAGING_DIR, and compare it to what we
   have saved at the configure step.

So regardless of whether a file has been installed in $(HOST_DIR)
during the target or staging installation steps of a target package,
or if a host package has installed a file in $(TARGET_DIR), we will
detect it.

The pkg_size_before and pkg_size_after macros are intentionally left
where they are (even if they now fall in the middle of the
GLOBAL_INSTRUMENTATION_HOOKS implementations) to minimize the diffstat
and facilitate review.

Note that we also have to change check_bin_arch to be explicitly
called from the install step rather than through a
GLOBAL_INSTRUMENTATION_HOOKS as it depends on the .files-list.txt file
produced by the pkg_size_after function.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>