crt: tests: update t_main_assert

It is unclear what is the purpose of t_main_assert; it could be a simple
test program to observe behavior of assert() in an application using `main`
as the entry point.

On Windows, `main` usually recieves at least one argument (argv[0]) which is
the absolute filename of the executable.

Update this test to check this assumption.

Add t_main_assert to testcases/Makefile.am.

Signed-off-by: Kirill Makurin <maiddaisuki@outlook.com>
Signed-off-by: LIU Hao <lh_mouse@126.com>