sanitizer_common: guard the wcslen interceptor code with SANITIZER_INTERCEPT_WCSLEN

[thurston]

Summary

This patch adds the #if SANITIZER_INTERCEPT_ guard for wcslen, similarly to how all the other
functions are guarded. It was the only missing SANITIZER_INTERCEPT_ guard [1].

This missing guard was discovered while investigating the stage2/hwasan check failure of https://reviews.llvm.org/D150708 ("hwasan: lay groundwork for importing subset of sanitizer_common interceptors [NFC]"), that was seen in https://lab.llvm.org/buildbot/#/builders/236/builds/4069. llvm_build_hwasan/unittests/ADT/./ADTTests had crashed with a backtrace of:
#0 0x0000000000000000 in ?? ()
#1 0x0000aaaaab20e058 in constexpr_wcslen () at /home/thurston/scratch_dir/libcxx_build_hwasan/include/c++/v1/cwchar:195
#2 length () at /home/thurston/scratch_dir/libcxx_build_hwasan/include/c++/v1/string/char_traits.h:311
#3 basic_string<0> () at /home/thurston/scratch_dir/libcxx_build_hwasan/include/c++/v1/string:904
#4 0x0000aaaaab20d800 in TestBody () at /home/thurston/scratch_dir/llvm-project/llvm/unittests/ADT/HashingTest.cpp:125
...
A disassembly of the binary showed that wcslen interception was present (since it was not guarded by SANITIZER_INTERCEPT_WCSLEN); howver, since INIT_WCSLEN was not called, REAL(wcslen) was null, resulting in the null pointer dereference.

[1] I checked this using "egrep '^#[ ]*define[ ]+(INIT_.*)' sanitizer_common_interceptors.inc | tr -s ' ' | sed -r 's/^# /#/' | cut -d ' ' -f 2 | sort | uniq -c | grep -v '^[ ]*2[ ]'"
The other matches are {INIT_PTHREAD_SETNAME_NP, INIT_QSORT, INIT_SHA2_INTECEPTORS(LEN), INIT_TLS_GET_ADDR, INIT_WAIT4}, which all have good reasons for not having exactly two cases.

compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc

INTERCEPTOR(int, mcheck_pedantic, void (*abortfunc)(int mstatus)) {
   return 0;
 }
 
 INTERCEPTOR(int, mprobe, void *ptr) {
   return 0;
 }
 #endif
 
+#if SANITIZER_INTERCEPT_WCSLEN
 INTERCEPTOR(SIZE_T, wcslen, const wchar_t *s) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, wcslen, s);
   SIZE_T res = REAL(wcslen)(s);
   COMMON_INTERCEPTOR_READ_RANGE(ctx, s, sizeof(wchar_t) * (res + 1));
   return res;
 }
 
 INTERCEPTOR(SIZE_T, wcsnlen, const wchar_t *s, SIZE_T n) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, wcsnlen, s, n);
   SIZE_T res = REAL(wcsnlen)(s, n);
   COMMON_INTERCEPTOR_READ_RANGE(ctx, s, sizeof(wchar_t) * Min(res + 1, n));
   return res;
 }
 #define INIT_WCSLEN                  \
   COMMON_INTERCEPT_FUNCTION(wcslen); \
   COMMON_INTERCEPT_FUNCTION(wcsnlen);
+#else
+#define INIT_WCSLEN
+#endif
 
 #if SANITIZER_INTERCEPT_WCSCAT
 INTERCEPTOR(wchar_t *, wcscat, wchar_t *dst, const wchar_t *src) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, wcscat, dst, src);
   SIZE_T src_size = internal_wcslen(src);
   SIZE_T dst_size = internal_wcslen(dst);
   COMMON_INTERCEPTOR_READ_RANGE(ctx, src, (src_size + 1) * sizeof(wchar_t));

compiler-rt/lib/sanitizer_common/sanitizer_platform_interceptors.h

 #define SANITIZER_INTERCEPT_MEMALIGN (!SI_FREEBSD && !SI_MAC && !SI_NETBSD)
 #define SANITIZER_INTERCEPT___LIBC_MEMALIGN SI_GLIBC
 #define SANITIZER_INTERCEPT_PVALLOC (SI_GLIBC || SI_ANDROID)
 #define SANITIZER_INTERCEPT_CFREE (SI_GLIBC && !SANITIZER_RISCV64)
 #define SANITIZER_INTERCEPT_REALLOCARRAY SI_POSIX
 #define SANITIZER_INTERCEPT_ALIGNED_ALLOC (!SI_MAC)
 #define SANITIZER_INTERCEPT_MALLOC_USABLE_SIZE (!SI_MAC && !SI_NETBSD)
 #define SANITIZER_INTERCEPT_MCHECK_MPROBE SI_LINUX_NOT_ANDROID
+#define SANITIZER_INTERCEPT_WCSLEN SI_POSIX
 #define SANITIZER_INTERCEPT_WCSCAT SI_POSIX
 #define SANITIZER_INTERCEPT_WCSDUP SI_POSIX
 #define SANITIZER_INTERCEPT_SIGNAL_AND_SIGACTION (!SI_WINDOWS && SI_NOT_FUCHSIA)
 #define SANITIZER_INTERCEPT_BSD_SIGNAL SI_ANDROID
 
 #define SANITIZER_INTERCEPT_ACCT (SI_NETBSD || SI_FREEBSD)
 #define SANITIZER_INTERCEPT_USER_FROM_UID SI_NETBSD
 #define SANITIZER_INTERCEPT_UID_FROM_USER SI_NETBSD