Allow to build with the PyPI package "clang" instead of "libclang". 1. It seems to be maintained. 2. In the FreeBSD base system there is no pre-built libclang.so. If you need this library you have to install llvm from ports additionally. 2. On FreeBSD there is no pre-built wheel "libclang" with a packaged libclang.so.

Short: a
Long: append
Help: Append to target file when uploading
Protocols: FTP SFTP
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When used in an upload, this makes curl append to the target file instead of
overwriting it. If the remote file doesn't exist, it will be created.  Note
that this flag is ignored by some SFTP servers (including OpenSSH).