[ASan] Disable allocator_oom_test.cc on s390

[alekseyshl]

Summary

ASan shadow memory on s390 is larger than other configurations, let's
disable this test for now (will revisit it later).

compiler-rt/trunk/test/asan/TestCases/Linux/allocator_oom_test.cc

 // RUN:   | FileCheck %s --check-prefixes=CHECK-REALLOC,CHECK-CRASH
 // RUN: %env_asan_opts=allocator_may_return_null=1     %run %t realloc 2>&1 \
 // RUN:   | FileCheck %s --check-prefixes=CHECK-REALLOC,CHECK-NULL
 // RUN: %env_asan_opts=allocator_may_return_null=0 not %run %t realloc-after-malloc 2>&1 \
 // RUN:   | FileCheck %s --check-prefixes=CHECK-MALLOC-REALLOC,CHECK-CRASH
 // RUN: %env_asan_opts=allocator_may_return_null=1     %run %t realloc-after-malloc 2>&1 \
 // RUN:   | FileCheck %s --check-prefixes=CHECK-MALLOC-REALLOC,CHECK-NULL
 
+// ASan shadow memory on s390 is too large for this test.
+// UNSUPPORTED: s390
+
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 #include <assert.h>
 
 int main(int argc, char **argv) {
   assert(argc == 2);
   const char *action = argv[1];