config/git: import suckless sbase

i currently use the output of sha512sum in several
places of xbmk, which is a bit unreliable in case
output changes.

other cases where i use util outputs in variables
are probably reliable, because i'm using mostly
posix utilities in those.

to mitigate this, i now import suckless sbase, which
has a reasonable sha512sum implementation.

*every* binary it builds is being placed in build.list,
because i'll probably start using more of them.

for example, i may start modifying the "date"
implementation, adding the GNU-specific options that
i need as mentioned on init.sh

i'm importing it in util/ because the sha512sum
util is needed for verifying project sources, so
if sbase itself is a "project source", that means
we can into a chicken and egg bootstrapping problem.

this is sbase at revision:
055cc1ae1b3a13c3d8f25af0a4a3316590efcd48

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/sbase/sha384sum.1

@@ -0,0 +1,32 @@
+.Dd February 24, 2016
+.Dt SHA384SUM 1
+.Os sbase
+.Sh NAME
+.Nm sha384sum
+.Nd compute or check SHA-384 message digests
+.Sh SYNOPSIS
+.Nm
+.Op Fl c
+.Op Ar file ...
+.Sh DESCRIPTION
+.Nm
+writes SHA-384 (384-bit) checksums of each
+.Ar file
+to stdout.
+If no
+.Ar file
+is given
+.Nm
+reads from stdin.
+.Sh OPTIONS
+.Bl -tag -width Ds
+.It Fl c
+Read list of SHA-384 checksums from each
+.Ar file
+and check them.
+If no
+.Ar file
+is given
+.Nm
+reads from stdin.
+.El