[3.12] pythongh-125301: Backport some test support helpers (is_apple_…

…mobile, is_apple) (pythonGH-125311)

(cherry picked from commit 391659b)

Lib/test/support/__init__.py

@@ -43,7 +43,7 @@
     "requires_limited_api", "requires_specialization",
     # sys
     "MS_WINDOWS", "is_jython", "is_android", "is_emscripten", "is_wasi",
-    "check_impl_detail", "unix_shell", "setswitchinterval",
+    "is_apple_mobile", "check_impl_detail", "unix_shell", "setswitchinterval",
     # os
     "get_pagesize",
     # network
@@ -531,7 +531,7 @@ def requires_legacy_unicode_capi():
 
 is_android = hasattr(sys, 'getandroidapilevel')
 
-if sys.platform not in ('win32', 'vxworks'):
+if sys.platform not in {"win32", "vxworks", "ios", "tvos", "watchos"}:
     unix_shell = '/system/bin/sh' if is_android else '/bin/sh'
 else:
     unix_shell = None
@@ -541,19 +541,35 @@ def requires_legacy_unicode_capi():
 is_emscripten = sys.platform == "emscripten"
 is_wasi = sys.platform == "wasi"
 
-has_fork_support = hasattr(os, "fork") and not is_emscripten and not is_wasi
+# Apple mobile platforms (iOS/tvOS/watchOS) are POSIX-like but do not
+# have subprocess or fork support.
+is_apple_mobile = sys.platform in {"ios", "tvos", "watchos"}
+is_apple = is_apple_mobile or sys.platform == "darwin"
+
+has_fork_support = hasattr(os, "fork") and not (
+    is_emscripten
+    or is_wasi
+    or is_apple_mobile
+)
 
 def requires_fork():
     return unittest.skipUnless(has_fork_support, "requires working os.fork()")
 
-has_subprocess_support = not is_emscripten and not is_wasi
+has_subprocess_support = not (
+    is_emscripten
+    or is_wasi
+    or is_apple_mobile
+)
 
 def requires_subprocess():
     """Used for subprocess, os.spawn calls, fd inheritance"""
     return unittest.skipUnless(has_subprocess_support, "requires subprocess support")
 
 # Emscripten's socket emulation and WASI sockets have limitations.
-has_socket_support = not is_emscripten and not is_wasi
+has_socket_support = not (
+    is_emscripten
+    or is_wasi
+)
 
 def requires_working_socket(*, module=False):
     """Skip tests or modules that require working sockets