fortran: Avoid infinite self-recursion [PR105381]

fortran: Avoid infinite self-recursion [PR105381]

Dummy array decls are local decls different from the argument decl
accessible through GFC_DECL_SAVED_DESCRIPTOR.  If the argument decl has
a DECL_LANG_SPECIFIC set, it is copied over to the local decl at the
time the latter is created, so that the DECL_LANG_SPECIFIC object is
shared between local dummy decl and argument decl, and thus the
GFC_DECL_SAVED_DESCRIPTOR of the argument decl is the argument decl
itself.

The r12-8230-g7964ab6c364c410c34efe7ca2eba797d36525349 change introduced
the non_negative_strides_array_p predicate which recurses through
GFC_DECL_SAVED_DESCRIPTOR to avoid seeing dummy decls as purely local
decls.  As the GFC_DECL_SAVED_DESCRIPTOR of the argument decl is itself,
this can cause infinite recursion.

This change adds a check to avoid infinite recursion.

	PR fortran/102043
	PR fortran/105381

gcc/fortran/ChangeLog:

	* trans-array.cc (non_negative_strides_array_p): Inline variable
	orig_decl and merge nested if conditions.  Add condition to not
	recurse if the next argument is the same as the current.

gcc/testsuite/ChangeLog:

	* gfortran.dg/character_array_dummy_1.f90: New test.