os: Use a trusted operating system entropy source.
This is the default method if such an entropy
source exists.
- getrandom: Use the L<getrandom(2)> system call if available.
+ getrandom: Use the L<getrandom(2)> or equivalent system
+ call.
devrandom: Use the the first device from the DEVRANDOM list
which can be opened to read random bytes. The
DEVRANDOM preprocessor constant expands to