fix(guix-bootstrap): wire mes seeds into bootstrap.scm and align xz seed link mode with Guix static bootstrap

steps-guix/xz-5.2.4/pass1.sh

@@ -2,6 +2,14 @@
 
 SEED_PREFIX="/bootstrap-seeds/xz-5.2.4"
 
+src_prepare() {
+    default
+
+    # Mirror Guix bootstrap static strategy: force libtool-built xz executable
+    # to link with -all-static.
+    sed -i 's/^xz_LDADD =/xz_LDADD = -all-static /' src/xz/Makefile.in
+}
+
 src_configure() {
     ./configure \
         --prefix="${SEED_PREFIX}" \