[testsuite] Introduce effective target non_strict_prototype

[testsuite] Introduce effective target non_strict_prototype

Consider test-case gcc.c-torture/compile/pr71109.c.

It contains a prototype-less declaration of foo:
...
static void foo ();
...
followed by a call to foo
...
      foo (bar, a);
...
followed by the definition of foo:
...
static inline void
foo (int x, struct S y, struct T z)
...

The test-case has undefined behaviour, but for the nvptx target it doesn't even
assemble:
...
$ gcc src/gcc/testsuite/gcc.c-torture/compile/pr71109.c -c
ptxas pr71109.o, line 196; error   : Type of argument does not match \
  formal parameter '%in_ar0'
ptxas pr71109.o, line 196; error   : Alignment of argument does not match \
  formal parameter '%in_ar0'
ptxas pr71109.o, line 196; error   : Call has wrong number of parameters
ptxas fatal   : Ptx assembly aborted due to errors
nvptx-as: ptxas returned 255 exit status
...

The problem is that this call:
...
   191  {
   192  .param .u64 %out_arg1;
   193  st.param.u64 [%out_arg1],%r23;
   194  .param .u64 %out_arg2;
   195  st.param.u64 [%out_arg2],%r32;
   196  call foo,(%out_arg1,%out_arg2);
   197  }
...
does not match the preceding declaration:
...
     6  // BEGIN FUNCTION DECL: foo
     7  .func foo (.param .u32 %in_ar0, .param .u64 %in_ar1, .param .u64 %in_ar2);
...
which is a PTX error.

Introduce an effective target non_strict_prototype that returns 0 for nvptx,
and use it in this and similar test-cases.

Tested on nvptx.

gcc/testsuite/ChangeLog:

	* lib/target-supports.exp (check_effective_target_non_strict_prototype):
	New proc.
	* gcc.c-torture/compile/pr71109.c: Require effective target
	non_strict_prototype.
	* gcc.c-torture/compile/pr83051-2.c: Same.
	* gcc.c-torture/compile/pr89663-1.c: Same.
	* gcc.c-torture/compile/pr89663-2.c: Same.
	* gcc.c-torture/compile/pr96796.c: Same.