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/rev.c

@@ -0,0 +1,74 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "text.h"
+#include "util.h"
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [file ...]\n", argv0);
+}
+
+static void
+rev(FILE *fp)
+{
+	static char *line = NULL;
+	static size_t size = 0;
+	size_t i;
+	ssize_t n;
+	int lf;
+
+	while ((n = getline(&line, &size, fp)) > 0) {
+		lf = n && line[n - 1] == '\n';
+		i = n -= lf;
+		for (n = 0; i--;) {
+			if (UTF8_POINT(line[i])) {
+				n++;
+			} else {
+				fwrite(line + i, 1, n + 1, stdout);
+				n = 0;
+			}
+		}
+		if (n)
+			fwrite(line, 1, n, stdout);
+		if (lf)
+			fputc('\n', stdout);
+	}
+}
+
+int
+main(int argc, char *argv[])
+{
+	FILE *fp;
+	int ret = 0;
+
+	ARGBEGIN {
+	default:
+		usage();
+	} ARGEND
+
+	if (!argc) {
+		rev(stdin);
+	} else {
+		for (; *argv; argc--, argv++) {
+			if (!strcmp(*argv, "-")) {
+				*argv = "<stdin>";
+				fp = stdin;
+			} else if (!(fp = fopen(*argv, "r"))) {
+				weprintf("fopen %s:", *argv);
+				ret = 1;
+				continue;
+			}
+			rev(fp);
+			if (fp != stdin && fshut(fp, *argv))
+				ret = 1;
+		}
+	}
+
+	ret |= fshut(stdin, "<stdin>") | fshut(stdout, "<stdout>");
+
+	return ret;
+}