VPATH build fails in "make check" step

Hi,

The newest snapshot, ncurses-6.6-20260808, fails the "make check" step
in a VPATH build (whereas it works fine in an in-tree build).

How to reproduce:

$ tar xfz ncurses.tar.gz
$ cd ncurses-6.6-20260808/
$ mkdir bb
$ cd bb/
$ ../configure --with-shared --enable-rpath --disable-lib-suffixes --enable-widec --with-pthread
$ make
$ make check
...
make[1]: Entering directory '/home/bruno/ncurses-6.6-20260808/bb/test'
** testing *.h
headers.c:1:10: fatal error: *.h: No such file or directory
    1 | #include <*.h>
      |          ^~~~~
compilation terminated.
make[1]: *** [Makefile:170: check] Error 1
make[1]: Leaving directory '/home/bruno/ncurses-6.6-20260808/bb/test'
make: *** [Makefile:137: check] Error 2


More info, to help the investigation:

This is on a GNU system (Ubuntu 26.04 to be precise).

In test/Makefile, the SHELL variable is defined to /bin/sh.

In the build dir 'bb/':
$ ls -1 test/*.h
(none)

In the source dir:
$ ls -1 test/*.h
test/color_name.h
test/dump_window.h
test/edit_field.h
test/linedata.h
test/parse_rgb.h
test/picsmap.h
test/popup_msg.h
test/test.priv.h
test/widechars.h

$ ls --version
ls (GNU coreutils) 9.11-pre


Best regards,

         Bruno