ww: driver/coordinator robustness — dirent errors, EINTR, block comments

Three same-cluster robustness holes. enumeratedir treated a failed
getdents64 (r<0) as EOF: a mid-walk error silently truncated the
package source list, and a first-read error was misdiagnosed as
"directory contains no WW package sources" -- it now routes the
caller's "cannot read directory" arm. run_test_bin's waitpid had no
EINTR retry and its return was unchecked, so an interrupted wait
left status==0 and reported a false test PASS (the do_run twin
already retried). The coordinator's pkgskipspace now also skips
/* */ before the package clause like the driver's sep_skip_space --
a source opening with a block comment built under ww but failed
coordinator discovery.

cmd/ww/main.c

@@ -72,7 +72,12 @@ run_test_bin(const char *bin, const char *pattern)
 		_exit(127);
 	}
 	int status = 0;
-	waitpid(pid, &status, 0);
+	/* the do_run twin's EINTR discipline: an interrupted wait left
+	 * status==0, so WIFEXITED(0)/WEXITSTATUS(0) reported a false
+	 * test PASS. */
+	pid_t got;
+	do { got = waitpid(pid, &status, 0); } while (got < 0 && errno == EINTR);
+	if (got < 0) { perror("ww: waitpid"); return -1; }
 	if (WIFEXITED(status)) return WEXITSTATUS(status);
 	return 1;
 }