coverage: better exposure for automake bug#12372 (tags-related)
Alas, in contrast with what is said in the commit message of previous
commit '
v1.12.3-14-g94b7b8e', that bug is still present also in the
current maint branch (which will become automake version 1.12.4); it
is just that it only triggers when a _SOURCES variable contains only
files with custom extension.
* t/tags-pr12372.sh: Extend.
* t/list-of-tests.mk: Add it.
Suggested-by: Юрий Пухальский <aikipooh@gmail.com>
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>