mkosi: configure multiarch libdir in debian/ubuntu builds

Debian/Ubuntu use /usr/lib/<triplet> instead of /usr/lib64, so configure it
accordingly. This is especially important for cryptsetup token plugins,
as cryptsetup comes from the distro and is configured to look into those
directories.

(cherry picked from commit bbb40c4e6f)

mkosi.build

@@ -86,7 +86,19 @@ if [ ! -f "$BUILDDIR"/build.ninja ] ; then
                 rootprefix=/${rootprefix#/}
         fi
 
+        # On debian-like systems the library directory is not /usr/lib64 but /usr/lib/<arch-triplet>/.
+        # It is important to use the right one especially for cryptsetup plugins, otherwise they will be
+        # installed in the wrong directory and not be found by cryptsetup. Assume native build.
+        if grep -q -e "ID=debian" -e "ID_LIKE=debian" /etc/os-release && command -v dpkg 2>/dev/null; then
+                LIBDIR="-Drootlibdir=/usr/lib/$(dpkg-architecture -qDEB_HOST_MULTIARCH)"
+                PAMDIR="-Dpamlibdir=/usr/lib/$(dpkg-architecture -qDEB_HOST_MULTIARCH)/security"
+        fi
+
+        # Cannot quote $LIBDIR and $PAMDIR, because they may be empty, and meson will fail.
+        # shellcheck disable=SC2086
         meson setup "$BUILDDIR" \
+                ${LIBDIR:-} \
+                ${PAMDIR:-} \
                 -D "sysvinit-path=$sysvinit_path" \
                 -D "rootprefix=$rootprefix" \
                 -D man=false \

mkosi.conf.d/debian/10-debian.conf

@@ -44,6 +44,7 @@ Packages=
 BuildPackages=
         bpftool
         docbook-xsl
+        dpkg-dev
         g++
         gcc-multilib
         libacl1-dev

mkosi.conf.d/ubuntu/10-ubuntu.conf

@@ -45,6 +45,7 @@ Packages=
 
 BuildPackages=
         docbook-xsl
+        dpkg-dev
         g++
         gcc-multilib
         libacl1-dev