system_get_version - get version string for system
#include <zircon/syscalls.h>
zx_status_t zx_system_get_version(char* version, size_t version_size);
zx_system_get_version() fills in the given character array with a string
identifying the version of the Zircon system currently running.
The provided size must be large enough for the complete string
including its null terminator.
The version string is guaranteed to never require more than 64 bytes of storage including the null terminator.
The first four characters identify the version scheme. An example of the string returned is "git-8a07d52603404521038d8866b297f99de36f9162".
TODO(ZX-2399)
zx_system_get_version() returns ZX_OK on success.
ZX_ERR_BUFFER_TOO_SMALL version_size is too short.