[libbacktrace] Don't assign check_PROGRAMS to TESTS
In automake files, the check_PROGRAMS variable lists programs that need to be
build for testing, and TESTS lists the programs that need to be run.
The libbacktrace/Makefile.am uses a shortcut:
...
TESTS = $(check_PROGRAMS)
...
to make sure that each program added with:
...
check_PROGRAMS += foo
...
is both build and run.
However, for the allocfail.sh test, we need allocfail to be build and
allocfail.sh to be run:
...
check_PROGRAMS += allocfail
TESTS += allocfail.sh
...
but the shortcut causes allocfail also to be run, which is not required.
Fix this by removing the short-cut, allowing check_PROGRAMS to retain its
original semantics, and introducing a variable BUILDTESTS for programs that
need to be both build and run.