Build the BearSSL library.
.Pp
BearSSL is a tiny SSL library suitable for embedded environments.
For details see
.Lk https://www.BearSSL.org/
.Pp
This library is currently only used to perform
signature verification and related operations
for Verified Exec and
.Xr loader 8 .
.Pp
Due to size constraints in the BIOS environment on x86, one may need to set
.Va LOADERSIZE
larger than the
default 500000, although often loader is under the 500k limit even with
this option.
Setting
.Va LOADERSIZE
larger than 500000 may cause
.Xr pxeboot 8
to be too large to work.
Careful testing of the loader in the target environment when built with a larger
limit to establish safe limits is critical because different BIOS environments
reserve differing amounts of the low 640k space, making a precise limit for
everybody impossible.
.Pp
See also
.Va WITH_LOADER_PXEBOOT
for other considerations.