[testsuite] Add missing require-effective-target allloca

Add missing require-effect-target alloca directives.

Tested on nvptx.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/pr92088-1.c: Add require-effective-target alloca.
	* gcc.dg/torture/pr92088-2.c: Same.
	* gcc.dg/torture/pr93124.c: Same.
	* gcc.dg/torture/pr94479.c: Same.
	* gcc.dg/tree-ssa/builtin-sprintf-warn-22.c: Same.

gcc/testsuite/gcc.dg/torture/pr92088-1.c

@@ -1,4 +1,5 @@
 /* { dg-do run } */
+/* { dg-require-effective-target alloca } */
 
 int __attribute__((noipa))
 g (char *p)

gcc/testsuite/gcc.dg/torture/pr92088-2.c

@@ -1,4 +1,5 @@
 /* { dg-do compile } */
+/* { dg-require-effective-target alloca } */
 
 void foo(int n)
 {

gcc/testsuite/gcc.dg/torture/pr93124.c

@@ -1,4 +1,5 @@
 /* { dg-additional-options "-fno-rerun-cse-after-loop -fno-guess-branch-probability -fno-tree-fre" } */
+/* { dg-require-effective-target alloca } */
 
 int x;
 

gcc/testsuite/gcc.dg/torture/pr94479.c

@@ -1,6 +1,7 @@
 /* { dg-do compile } */
 /* { dg-require-stack-check "specific" } */
 /* { dg-additional-options "-fstack-check -w" } */
+/* { dg-require-effective-target alloca } */
 
 int a;
 struct b {

gcc/testsuite/gcc.dg/tree-ssa/builtin-sprintf-warn-22.c

@@ -1,7 +1,8 @@
 /* PR tree-optimization/91567 - Spurious -Wformat-overflow warnings building
    glibc (32-bit only)
    { dg-do compile }
-   { dg-options "-O2 -Wall -ftrack-macro-expansion=0" } */
+   { dg-options "-O2 -Wall -ftrack-macro-expansion=0" }
+   { dg-require-effective-target alloca } */
 
 typedef __SIZE_TYPE__ size_t;