[sanitizer] Add type __sanitizer::ssize (llvm#116957)

Since the sanitizer merge in commit r15-5164-gfa321004f3f628 of GCC
which entails LLVM commit 61a6439, GCCs
bootstrap is broken on s390 -m31. This is due to commit
ec68dc1 which introduces stricter type
checking which is why GCC bootstrap fails with

```
In file included from /gcc/src/libsanitizer/interception/interception.h:18,
                 from /gcc/src/libsanitizer/interception/interception_type_test.cpp:14:
/gcc/src/libsanitizer/interception/interception_type_test.cpp:30:61: error: static assertion failed
   30 | COMPILER_CHECK((__sanitizer::is_same<::SSIZE_T, ::ssize_t>::value));
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
/gcc/src/libsanitizer/sanitizer_common/sanitizer_internal_defs.h:363:44: note: in definition of macro 'COMPILER_CHECK'
  363 | #define COMPILER_CHECK(pred) static_assert(pred, "")
      |                                            ^~~~
make[8]: *** [Makefile:469: interception_type_test.lo] Error 1
```

The culprit seems to be that we don't check for equality of type sizes
anymore but rather whether the types are indeed the same. On s390 -m31
we have that `sizeof(int)==sizeof(long)` holds which is why previously
the checks succeeded. They fail now because

```
size_t      => unsigned long
ssize_t     => long
ptrdiff_t   => int
::SSIZE_T   => __sanitizer::sptr => int
::PTRDIFF_T => __sanitizer::sptr => int
```

This is fixed by mapping `SSIZE_T` to `long` in the end.

```
#if defined(__s390__) && !defined(__s390x__)
typedef long ssize;
#else
typedef sptr ssize;
#endif

#define SSIZE_T __sanitizer::ssize
```

Author: stefan-sf-ibm

compiler-rt/lib/interception/interception.h

@@ -37,7 +37,7 @@
 #endif
 
 #define SIZE_T __sanitizer::usize
-#define SSIZE_T __sanitizer::sptr
+#define SSIZE_T __sanitizer::ssize
 typedef __sanitizer::sptr    PTRDIFF_T;
 typedef __sanitizer::s64     INTMAX_T;
 typedef __sanitizer::u64     UINTMAX_T;

compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h

@@ -203,6 +203,12 @@ typedef __SIZE_TYPE__ usize;
 typedef uptr usize;
 #endif
 
+#if defined(__s390__) && !defined(__s390x__)
+typedef long ssize;
+#else
+typedef sptr ssize;
+#endif
+
 typedef u64 tid_t;
 
 // ----------- ATTENTION -------------