The function assumed that the raw output of "adb get-serialno" was a
NUL-terminated string, but it is not the case.
It this output did not end with a space or a new line character, then
sc_str_truncate() would write '\0' over the last character. Even worse,
if the output was empty, then sc_str_truncate() would write
out-of-bounds.
Avoid the error-prone sc_str_truncate() util function.
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