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/libutil/sha224.c

@@ -0,0 +1,26 @@
+/* public domain sha224 implementation based on fips180-3 */
+#include <stdint.h>
+#include "../sha224.h"
+
+extern void sha256_sum_n(void *, uint8_t *, int n);
+
+void
+sha224_init(void *ctx)
+{
+	struct sha224 *s = ctx;
+	s->len = 0;
+	s->h[0] = 0xc1059ed8;
+	s->h[1] = 0x367cd507;
+	s->h[2] = 0x3070dd17;
+	s->h[3] = 0xf70e5939;
+	s->h[4] = 0xffc00b31;
+	s->h[5] = 0x68581511;
+	s->h[6] = 0x64f98fa7;
+	s->h[7] = 0xbefa4fa4;
+}
+
+void
+sha224_sum(void *ctx, uint8_t md[SHA224_DIGEST_LENGTH])
+{
+	sha256_sum_n(ctx, md, 8);
+}