libuv: Restore compilation on Apple i386 architecture

libuv upstream commit `2475296c` (build: make code compilable for iOS on
Xcode, 2020-01-18, v1.35.0~47) added a `defined(TARGET_OS_IPHONE)`
preprocessor condition, but `TARGET_OS_IPHONE` is always defined on
Apple to either 0 or 1.

Utilities/cmlibuv/src/unix/core.c

@@ -521,7 +521,7 @@ int uv__close_nocancel(int fd) {
 #if defined(__APPLE__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdollar-in-identifier-extension"
-#if defined(__LP64__) || defined(TARGET_OS_IPHONE)
+#if defined(__LP64__) || TARGET_OS_IPHONE
   extern int close$NOCANCEL(int);
   return close$NOCANCEL(fd);
 #else