BUILT_SOURCES does not uses

[Akim Demaille]

The appended test fails, pretending that LOCAL_BUILT_SOURCES is not
used, although it is, by BUILT_SOURCES.  Note that the same happens
with MAINTAINERCLEANFILES.  I have not tried other such magic vars.

src/am/tests % ./warnopts2.test                                  nostromo Err 1
/home/akim/src/am/tests:/home/akim/bin:/home/lrde/lrde/usr/bin:/home/akim/bin:/home/lrde/lrde/usr/bin:/home/akim/bin:/home/lrde/lrde/usr/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games:/usr/X11R6/bin:/usr/local/kde/bin
=== Running test ./warnopts2.test
++ pwd
/home/akim/src/am/tests/testSubDir
+ set -e
+ cat
+ aclocal-1.8a
+ automake-1.8a --foreign -Werror -Wall
Makefile.am:2: unused variable: `LOCAL_BUILT_SOURCES'

warnopts2.test
Description: Binary data