Make make distcheck pass

`make distcheck` was failing on the `check` task during the VPATH build
due to two reasons:

1. The `tests/*.t` and `tests/test.sh` were missing in the distribution.
2. The `T_LOG_COMPILER` command could not find the file `tests/test.sh`
since it was located in the source directory, not the build directory.

Makefile.am

@@ -16,9 +16,9 @@ TESTS=tests/01.t tests/02.t tests/03.t tests/04.t tests/05.t tests/06.t \
       tests/37.t tests/38.t tests/39.t tests/40.t tests/41.t tests/42.t \
       tests/43.t
 TEST_EXTENSIONS=.t
-T_LOG_COMPILER=sh tests/test.sh
+T_LOG_COMPILER=sh $(top_srcdir)/tests/test.sh
 check_PROGRAMS=tests/pick-test
-tests_pick_test_SOURCES=tests/pick-test.c
+tests_pick_test_SOURCES=$(TESTS) tests/test.sh tests/pick-test.c
 # Required by posix_openpt on Linux.
 tests_pick_test_CFLAGS=-D_XOPEN_SOURCE=600