glibc: Provide script to update glibv-2.25-1 to 2.26-0.

This is required, because a plain "bee update" is not
an atomic operation and would create incompatible
versions of ld-linux-x86-64.so.2 and libc.so.6
in the system and prevent the "bee update" to run
to cpmpletion.

scripts/update-glibc-to-2.26.sh

@@ -0,0 +1,65 @@
+#! /bin/sh
+
+# Script to update glibc-2.25-1 to glibc-2.26-0
+#
+# 2.25 ld-linux-x86-64.so.2 does not work with 2.26 libc.so.6 and visa versa
+# plus there are a lot of other incompatibilities beween libraries  provided
+# by different glibc packages.
+#
+# This scripts attempts to switch the versions of conflicting shared libraries
+# in a single atomic filesystem operation.
+
+set -e
+
+# same as "ln -sfT" but with a single rename() system call
+# instead of unlink();symlink(); as "ln -sfT" would do.
+#
+function replace_with_symlink() {
+	local target="$1"
+	local linkname="$2"
+
+	ln -sfT "$target" "$linkname.NEW"
+	mv -fT "$linkname.NEW" "$linkname"
+}
+
+function die() {
+    echo "$@" >&2
+    exit 1
+}
+
+cd /lib
+
+mkdir -p .glibc-switch/2.25 .glibc-switch/2.26
+(cd .glibc-switch/2.25 && tar xpf /src/mariux/beeroot/packages/glibc-2.25-1.x86_64.bee.tar.bz2)
+(cd .glibc-switch/2.26 && tar xpf /src/mariux/beeroot/packages/glibc-2.26-0.x86_64.bee.tar.bz2)
+ln -sfT 2.25 /lib/.glibc-switch/current
+
+# This link was accidentally omitted from glibc-2.25-1
+test -e .glibc-switch/2.25/lib/ld-linux-x86-64.so.2 || ln -s ld-2.25.so .glibc-switch/2.25/lib/ld-linux-x86-64.so.2
+
+cd .glibc-switch/2.26
+for f in $(find lib usr/lib -name "*.so*"); do
+  if [[ -e /$f ]]   # library exists in system
+  then
+    if [[
+      $(stat -L --print "%s.%y" "/$f") != $(stat -L --print "%s.%y" "$f")  # is not from the new glibc
+      && !(-L /$f && $(readlink "/$f") == /lib/.glibc-switch/*)            # and is not already a version switcher symlink
+     ]]; then
+        # replace library by symlink to current (old) glibc version
+        test -e /lib/.glibc-switch/current/$f || die "$f: not found in old glibc"
+        echo replace_with_symlink "/lib/.glibc-switch/current/$f" "/$f"
+        replace_with_symlink "/lib/.glibc-switch/current/$f" "/$f"
+    fi
+  else
+    # provide new library in system
+    echo ln -fT "$f" "/$f"
+    ln -fT "$f" "/$f"
+  fi
+done
+
+# now switch to new version
+replace_with_symlink 2.26 /lib/.glibc-switch/current
+
+# fixup
+bee update glibc-2.26-0.x86_64
+rm -r /lib/.glibc-switch