[llvm-libc] support for 64b long double (i386-linux-android)

[nickdesaulniers]

Filing an issue distinct from #110894. Android i386 uses long double == double, so __SIZEOF_LONG_DOUBLE__ is 8, not 12 as on i386-linux-gnu.

https://developer.android.com/ndk/guides/abis#x86
https://godbolt.org/z/e35cEK4fM

I'm going to explicitly error for this case in #115084, then revisit that this works as expected in a future patch. Filing a bug for the TODO.

[llvmbot]

@llvm/issue-subscribers-libc

Author: Nick Desaulniers (nickdesaulniers)

Filing an issue distinct from https://github.com//issues/110894. Android i386 uses `long double == double`, so `__SIZEOF_LONG_DOUBLE__` is `8`, not `12` as on i386-linux-gnu.

https://developer.android.com/ndk/guides/abis#x86
https://godbolt.org/z/e35cEK4fM

I'm going to explicitly error for this case in #115084, then revisit that this works as expected in a future patch. Filing a bug for the TODO.