Merge upstream changes

[fwcd]

Building the current version of the repo as described in https://github.com/apple/swift/blob/main/docs/Android.md#1-downloading-or-building-the-swift-android-stdlib-dependencies yields the following error:

checking whether the C compiler works... no
configure: error: in `.../libiconv-libicu-android/armeabi-v7a/icu/source':
configure: error: C compiler cannot create executables
See `config.log' for more details
+ exit 1

This bug seems to be known (see https://bugs.swift.org/browse/SR-14049), but unaddressed. For this reason, this PR merges the upstream changes from https://github.com/pelya/libiconv-libicu-android, which seem to at least successfully build the libraries using NDK r21e.