Fix srcdir computation for manual runs of old tests.

[Ralf Wildenhues]

When we moved to nonrecursive makefile setup in Libtool, running the
old testsuite tests manually ceased to work:

$ VERBOSE=yes ../libtool/tests/sh.test ; echo $?
sh.test: ===  Running sh.test
/bin/grep: /tmp/libtool/tests/libltdl/config/ltmain.m4sh: No such file or 
directory
[...]
1

I'm pushing the patch below to fix that regression:

$ make all tests/defs; VERBOSE=yes ../libtool/tests/sh.test; echo $?
0

(And yes, executing them from $top_builddir/tests does not work before
nor after this patch.)

Cheers,
Ralf

    Fix srcdir computation for manual runs of old tests.
    
    * tests/defs.m4sh: Strip trailing `/tests' from srcdir, to allow
    `$srcdir/tests/FOO.test' to be run from the top build directory.

diff --git a/tests/defs.m4sh b/tests/defs.m4sh
index 58296da..1230555 100644
--- a/tests/defs.m4sh
+++ b/tests/defs.m4sh
@@ -2,7 +2,7 @@ AS_INIT[]m4_divert_push([HEADER-COPYRIGHT])dnl
 # @configure_input@
 # defs -- Defines for Libtool testing environment.
 #
-#   Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009 Free Software
+#   Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009, 2010 Free Software
 #   Foundation, Inc.
 #   Written by Gord Matzigkeit, 1996
 #   Rewritten by Gary V. Vaughan, 2003
@@ -59,7 +59,7 @@ DEBUG | debug )
 esac
 
 if test -z "$srcdir"; then
-  srcdir=`$ECHO "$0" | $SED "$dirname"`
+  srcdir=`$ECHO "$0" | $SED "$dirname; s,/tests\$,,"`
   test "$srcdir" = "$0" && srcdir=.
 fi