non-recursive-gnulib-prefix-hack: Remove obsolete code

[Bruno Haible]

The non-recursive-gnulib-prefix-hack module contains code to transform
t-$@ patterns. But such patterns don't exist any more nowadays (probably
for several years already). So, let me remove this obsolete code.


2021-12-15  Bruno Haible  <bruno@clisp.org>

        non-recursive-gnulib-prefix-hack: Remove obsolete code.
        * build-aux/prefix-gnulib-mk (prefix): Remove handling of t-$@ pattern.

diff --git a/build-aux/prefix-gnulib-mk b/build-aux/prefix-gnulib-mk
index 347ddcd64..7b43eb0db 100755
--- a/build-aux/prefix-gnulib-mk
+++ b/build-aux/prefix-gnulib-mk
@@ -193,10 +193,6 @@ sub prefix ($)
   #   test '$(srcdir)' = . || rm -f $(top_builddir)/GNUmakefile
   s{\$\(srcdir\)/}{\$(top_srcdir)/$prefix}g;
 
-  # Sometimes, t-$@ is used instead of $@-t, which, of course, does
-  # not work when we have a $@ with a directory in it.
-  s{t-\$\@}{\$\@-t}g;
-
   # Some AC_SUBST patterns remain and would better be Make macros.
   s{\@(MKDIR_P)\@}{\$($1)}g;