Android NDK 18b issues

[tito]

Libffi latest stable version is incompatible with Android NDK 18b:

../src/arm/sysv.S:363:2: error: invalid instruction, did you mean: fldmiax?
 fldmiadgt ip, {d0-d7}
 ^
../src/arm/sysv.S:399:2: error: invalid instruction
 stmeqia r2, {r0, r1}
 ^
../src/arm/sysv.S:412:2: error: invalid instruction, did you mean: fstmiax?
 fstmiadeq r2, {d0-d3}
 ^
/tmp/sysv-5d4296.s:263:2: error: invalid instruction
 fstmfdd sp!, {d0-d7}
 ^
/tmp/sysv-5d4296.s:313:2: error: invalid instruction, did you mean: fldmiax?
 fldmiad sp, {d0-d1}
 ^
/tmp/sysv-5d4296.s:316:2: error: invalid instruction, did you mean: fldmiax?
 fldmiad sp, {d0-d3}

It appears to be because of clang 7.0, which doesn't accept deprecated functions.
The Android libffi version have fixes: https://android.googlesource.com/platform/external/libffi/+/ca22c3cb49a8cca299828c5ffad6fcfa76fdfa77

Didn't tested if libffi master have the fixes, but stable don't.

[ghost]

Has this been resolved with r18c or a newer libffi release? I've never seen these problems even using libffi, so maybe we can just tell people to use r18c and it'll work fine for the future

[inclement]

I found this still happened with NDK 19 in #1612, so we'll need to deal with this it seems.

[dbrnz]

FYI, libffi can be made to compile with NDK 19 by setting version = 3.3-rc0 and patches = [] in the libffi recipe.

[inclement]

Thanks @dbrnz, that's great to know.

[misl6]

Fixed via #1722