Save 10 bytes or so, last_patch_70 from Vladimir N. Oleynik
diff --git a/libbb/last_char_is.c b/libbb/last_char_is.c
index 4e2ee92..9bd7099 100644
--- a/libbb/last_char_is.c
+++ b/libbb/last_char_is.c
@@ -28,13 +28,11 @@
  */
 char * last_char_is(const char *s, int c)
 {
-	char *sret;
-	if (!s)
-	    return NULL;
-	sret  = (char *)s+strlen(s)-1;
-	if (sret>=s && *sret == c) { 
-		return sret;
-	} else {
-		return NULL;
+	char *sret = (char *)s;
+	if (sret) {
+		sret = strrchr(sret, c);
+		if(sret != NULL && *(sret+1) != 0)
+			sret = NULL;
 	}
+	return sret;
 }