[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.

gcc/testsuite/gcc.c-torture/compile/pr71109.c

@@ -1,4 +1,5 @@
 /* PR tree-optimization/71109 */
+/* { dg-require-effective-target non_strict_prototype } */
 
 struct S { int g, h; signed char i; int j; signed char k; int l[4]; } a, c;
 struct T { signed char g; } e;

gcc/testsuite/gcc.c-torture/compile/pr83051-2.c

@@ -1,4 +1,6 @@
 /* { dg-options "-fno-early-inlining" } */
+/* { dg-require-effective-target non_strict_prototype } */
+
 void
 bar ()
 {

gcc/testsuite/gcc.c-torture/compile/pr89663-1.c

@@ -1,4 +1,5 @@
 /* PR middle-end/89663 */
+/* { dg-require-effective-target non_strict_prototype } */
 
 int irint ();
 long lrint ();

gcc/testsuite/gcc.c-torture/compile/pr89663-2.c

@@ -1,5 +1,6 @@
 /* PR middle-end/89663 */
 /* { dg-require-effective-target indirect_calls } */
+/* { dg-require-effective-target non_strict_prototype } */
 
 int irint (double);
 long lrint (double);

gcc/testsuite/gcc.c-torture/compile/pr96796.c

@@ -1,4 +1,5 @@
 /* { dg-additional-options "-fcommon" } */
+/* { dg-require-effective-target non_strict_prototype } */
 
 struct S0 {
   signed f0 : 8;

gcc/testsuite/lib/target-supports.exp

@@ -10486,6 +10486,18 @@ proc check_effective_target_large_initializer { } {
 
     return 1
 }
+
+# Return 1 if the target allows function prototype mismatches
+# in the assembly.
+
+proc check_effective_target_non_strict_prototype { } {
+    if { [istarget nvptx*-*-*] } {
+	return 0
+    }
+
+    return 1
+}
+
 # Returns 1 if the target toolchain supports extended
 # syntax of .symver directive, 0 otherwise.