Thanks for fixing the problem with spaces in the home directory name on Windows.
Unfortunately, the Composer update still fails with the following error:
====Updating Composer...====
Updating to version 1.8.6 (stable channel).
Downloading (connecting...)
[RuntimeException]
SHA384 is not supported by your openssl extension, could not verify the phar file integrity
self-update [-r|--rollback] [--clean-backups] [--no-progress] [--update-keys] [--stable] [--preview] [--snapshot] [--set-channel-only] [--] [<version>]
====composer command completed with exit code -1====