Fixed unpack-tarballs handling of masterfiles tarballs

The symlink step was failing due to the tarball itself matching the glob

Ticket: none
Changelog: none
(cherry picked from commit f3c42b2)

Author: craigcomstock

build-scripts/unpack-tarballs

@@ -62,9 +62,11 @@ cd "$BASEDIR"
 gzip -dc $SOURCE_TARBALL | tar -xf -
 ln -s cfengine-3* core
 
-log_debug "UNPACKING MASTERFILES TARBALL AND SYMLINKING masterfiles/"
+log_debug "UNPACKING MASTERFILES TARBALL: $MASTERFILES_TARBALL AND SYMLINKING masterfiles/"
 # shellcheck disable=SC2086
 # > Double quote to prevent globbing and word splitting.
 # We want globbing here
 gzip -dc $MASTERFILES_TARBALL | tar -xf -
-ln -s cfengine-masterfiles-* masterfiles
+# the masterfiles tarball would match cfengine-masterfiles-* so find the unpacked dir specifically
+_cfmpfdir=$(find -type d -name 'cfengine-masterfiles-*')
+ln -s "$_cfmpfdir" masterfiles