Allow running on a cross-compiled rootfs

Allow running on a cross-compiled rootfs

For the shell scripts, new environment variables were introduced.

dracutsysrootdir is the root directory, file existence checks use it.

DRACUT_LDCONFIG can override ldconfig with a different one that works
on the sysroot with foreign binaries.

DRACUT_LDD can override ldd with a different one that works
with foreign binaries.

DRACUT_TESTBIN can override /bin/sh. A cross-compiled sysroot
may use symlinks that are valid only when running on the target
so a real file must be provided that exist in the sysroot.

DRACUT_INSTALL now supports debugging dracut-install in itself
when run by dracut but without debugging the dracut scripts.
E.g. DRACUT_INSTALL="valgrind dracut-install or
DRACUT_INSTALL="dracut-install --debug".

DRACUT_COMPRESS_BZIP2, DRACUT_COMPRESS_LBZIP2, DRACUT_COMPRESS_LZMA,
DRACUT_COMPRESS_XZ, DRACUT_COMPRESS_GZIP, DRACUT_COMPRESS_PIGZ,
DRACUT_COMPRESS_LZOP, DRACUT_COMPRESS_ZSTD, DRACUT_COMPRESS_LZ4,
DRACUT_COMPRESS_CAT: All of the compression utilities may be
overridden, to support the native binaries in non-standard places.

DRACUT_ARCH overrides "uname -m".

SYSTEMD_VERSION overrides "systemd --version".

The dracut-install utility was overhauled to support sysroot via
a new option -r and fixes for clang-analyze. It supports
cross-compiler-ldd from
https://gist.github.com/jerome-pouiller/c403786c1394f53f44a3b61214489e6f

DRACUT_INSTALL_PATH was introduced so dracut-install can work with
a different PATH. In a cross-compiled environment (e.g. Yocto), PATH
points to natively built binaries that are not in the host's /bin,
/usr/bin, etc. dracut-install still needs plain /bin and /usr/bin
that are relative to the cross-compiled sysroot.

The hashmap pool allocate_tile/deallocate_tile code was removed
because clang-analyze showed errors in it. hashmap_copy was removed
because it wasn't used and clang-analyze showed errors in it.

DRACUT_INSTALL_LOG_TARGET and DRACUT_INSTALL_LOG_LEVEL were
introduced so dracut-install can use different settings from
DRACUT_LOG_TARGET and DRACUT_LOG_LEVEL.

Signed-off-by: Böszörményi Zoltán <zboszor@pr.hu>