emul: add sanity check for blkfs

The man page says it's not always available and it caused problems
under some FSes. The condition is not needed in the context of
blk/, let's scrap it.

emul/emul.c

@@ -86,6 +86,13 @@ Machine* emul_init()
         fprintf(stderr, "Can't open\n");
         return NULL;
     }
+    fseek(blkfp, 0, SEEK_END);
+    if (ftell(blkfp) < 100 * 1024) {
+        fclose(blkfp);
+        fprintf(stderr, "emul/blkfs too small, something's wrong, aborting.\n");
+        return NULL;
+    }
+    fseek(blkfp, 0, SEEK_SET);
     // initialize memory
     memset(m.mem, 0, 0x10000);
     FILE *bfp = fopen(FBIN_PATH, "r");

tools/blkpack.c

@@ -29,9 +29,6 @@ int main(int argc, char *argv[])
         if ((strcmp(ep->d_name, ".") == 0) || strcmp(ep->d_name, "..") == 0) {
             continue;
         }
-        if (ep->d_type != DT_REG) {
-            continue;
-        }
         int blkid = atoi(ep->d_name);
         if (blkid >= blkcnt) {
             int newcnt = blkid+1;