Skip "arch" test if it's not built.

Skip "arch" test if it's not built.

* tests/misc/Makefile.am (built_programs): Define.
(TESTS_ENVIRONMENT): Add $(built_programs), for...
* tests/misc/arch: ...this: skip the test if arch is not built.
* src/Makefile.am (built_programs.list): New rule.
* tests/Makefile.am (built_programs): Rename from all_programs.
(TESTS_ENVIRONMENT): Use built_programs, not all_programs.
* tests/help-version: Likewise.
* NEWS: Mention that using --enable-no-install-program=X may
cause "make check" to fail.

Signed-off-by: Jim Meyering <jim@meyering.net>