stdbuf: fix automake variable name to work with cutting edge automake
* src/Makefile.am (pkglibexec_PROGRAMS): Rename from pkglib_PROGRAMS.
The latter is invalid. Without this change, automake
v1.11-373-g9ca6326 and newer (on master) would fail with this:
`pkglibdir' is not a legitimate directory for `PROGRAMS'
This changes the default installation directory of libstdbuf.so from
$prefix/lib/coreutils/ to
$prefix/libexec/coreutils/
* src/stdbuf.c (set_LD_PRELOAD): Search in PKGLIBEXECDIR, not PKGLIBDIR,
since that's where we install libstdbuf.so.
Do not search in "", the system default search path.