Fix statx feature test for Android

statx syscall was introduced in Android-30.
Compiling for Android<30 should fail, yet it doesn't, which results in false positive for a feature that is actually not available.
Would guess that this happens because of the same name for both the function and the struct, which is not #ifdef'ed for legacy Android.

Current check "host_system != 'android'" doesn't guard the feature test against android,
because host_system is never just android, it's android-$abi, like android-x86_64.
10 jobs for Android-statx-feature-test in 9 minutes and 43 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Style Check
passed #1082791
check-todos

00:01:21

passed #1082790
style-check-diff

00:01:27

 
  Build
passed #1082794
cross-android_api21_arm64

00:01:27

passed #1082795
cross-android_api28_arm64

00:01:27

passed #1082796
cross-mingw64

00:02:04

passed #1082793
debian-stable-x86_64

00:02:09

passed #1082792
fedora-x86_64

00:08:08

passed #1082797
win32-ps
msys2-mingw32

00:07:32

passed #1082798
win32-ps
vs2017-x64

00:08:07

 
  Coverage
passed #1082799
coverage

00:01:34

76.1%