[hwasan] Fix build breakage (-Wunused-function) in hwasan_interceptors.cpp (NFC)

In file included from /data/llvm-project/compiler-rt/lib/hwasan/hwasan_interceptors.cpp:141:
/data/llvm-project/compiler-rt/lib/hwasan/../sanitizer_common/sanitizer_common_interceptors.inc:1044:13: error: unused function 'write_iovec' [-Werror,-Wunused-function]
static void write_iovec(void *ctx, struct __sanitizer_iovec *iovec,
            ^
/data/llvm-project/compiler-rt/lib/hwasan/../sanitizer_common/sanitizer_common_interceptors.inc:1053:13: error: unused function 'read_iovec' [-Werror,-Wunused-function]
static void read_iovec(void *ctx, struct __sanitizer_iovec *iovec,
            ^
/data/llvm-project/compiler-rt/lib/hwasan/../sanitizer_common/sanitizer_common_interceptors.inc:10363:13: error: unused function 'InitializeCommonInterceptors' [-Werror,-Wunused-function]
static void InitializeCommonInterceptors() {
            ^
3 errors generated.