gh-140239: Check for statx on Android (#140395)

Android has Linux's statx, but MACHDEP is "android" on Android, so
configure doesn't check for statx on Android.  Base the check for statx
on ac_sys_system instead, which is "Linux-android" on Android, "Linux"
on other Linux distributions, and "AIX" on AIX (which has an
incompatible function named statx).

Author: jbosboom

Misc/NEWS.d/next/Build/2025-10-17-11-33-45.gh-issue-140239._k-GgW.rst

@@ -1 +1 @@
-Check ``statx`` availability only in Linux platforms
+Check ``statx`` availability only on Linux (including Android).

configure

@@ -5258,10 +5258,11 @@ AC_CHECK_FUNCS([ \
   wait wait3 wait4 waitid waitpid wcscoll wcsftime wcsxfrm wmemcmp writev \
 ])
 
-# Check statx availability in Linux
-if test "$MACHDEP" = "linux"; then
-  AC_CHECK_FUNCS([statx])
-fi
+# os.statx uses Linux's statx function.  AIX also has a function named statx,
+# but it's unrelated.  Check only on Linux (including Android).
+AS_CASE([$ac_sys_system],
+  [Linux*], [AC_CHECK_FUNCS([statx])]
+)
 
 # Force lchmod off for Linux. Linux disallows changing the mode of symbolic
 # links. Some libc implementations have a stub lchmod implementation that always