Add FATFS build test workflow #219

Job	Run time
Build wolfssl (ubuntu-latest)	5s
Build wolfssl (macos-latest)	5s
Build wolfssh (ubuntu-latest)	16s
Build wolfssh (ubuntu-latest, --enable-all)	20s
Build wolfssh (ubuntu-latest, --enable-sftp)	17s
Build wolfssh (ubuntu-latest, --enable-scp)	23s
Build wolfssh (ubuntu-latest, --enable-shell)	21s
Build wolfssh (macos-latest)	32s
Build wolfssh (macos-latest, --enable-all)	31s
Build wolfssh (macos-latest, --enable-sftp)	4s
Build wolfssh (macos-latest, --enable-scp)	34s
Build wolfssh (macos-latest, --enable-shell)	5s
	3m 33s

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