[NFC][libc++] Fix _LIBCPP_HAS_BITSCAN64 usage.

Seems line was accidentally left in
llvm-svn: 290924 86eebc5b658b5c2ccf2f4fbc16e8aee9880919a5

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D97211

diff --git a/libcxx/include/__bits b/libcxx/include/__bits
index 0d321da..c23203b 100644 (file)
--- a/libcxx/include/__bits
+++ b/libcxx/include/__bits
@@ -76,7 +76,6 @@ inline _LIBCPP_INLINE_VISIBILITY
 int __libcpp_ctz(unsigned long long __x) {
     unsigned long __where;
 #if defined(_LIBCPP_HAS_BITSCAN64)
-    (defined(_M_AMD64) || defined(__x86_64__))
   if (_BitScanForward64(&__where, __x))
     return static_cast<int>(__where);
 #else