Fix MAX 32 bit build problem described in libgit2/libgit2#2917
diff --git a/src/integer.h b/src/integer.h
index 8e86a48..b08094c 100644
--- a/src/integer.h
+++ b/src/integer.h
@@ -58,7 +58,7 @@ GIT_INLINE(bool) git__add_uint64_overflow(uint64_t *out, uint64_t one, uint64_t
#if (SIZE_MAX == UINT_MAX) && __has_builtin(__builtin_uadd_overflow)
# define git__add_sizet_overflow(out, one, two) \
__builtin_uadd_overflow(one, two, out)
-# define git__multiply_sizet_overflow(out, one, two)
+# define git__multiply_sizet_overflow(out, one, two) \
__builtin_umul_overflow(one, two, out)
#elif (SIZE_MAX == ULONG_MAX) && __has_builtin(__builtin_uaddl_overflow)
# define git__add_sizet_overflow(out, one, two) \