test: make popen.test tap-compatible

Part of #7618

NO_DOC=internal
NO_CHANGELOG=internal

test/unit/popen.c

@@ -2,6 +2,8 @@
 #include <stdlib.h>
 
 #include "trivia/util.h"
+
+#define UNIT_TAP_COMPATIBLE 1
 #include "unit.h"
 
 #include "coio.h"

test/unit/popen.result

-1..3
-	*** main_f ***
-    1..6
-	*** popen_write_exit ***
-    ok 1 - popen_new
-    ok 2 - state alive
-    ok 3 - write flag check
-    ok 4 - write to pipe
-    ok 5 - child exited
-    ok 6 - popen_delete
-	*** popen_write_exit: done ***
-ok 1 - subtests
-    1..5
-	*** popen_read_exit ***
-    ok 1 - popen_new
-    ok 2 - child exited
-    ok 3 - read flag check
-    ok 4 - read from pipe
-    ok 5 - popen_delete
-	*** popen_read_exit: done ***
-ok 2 - subtests
-    1..4
-	*** popen_kill ***
-    ok 1 - popen_new
-    ok 2 - popen_send_signal
-    ok 3 - child terminated
-    ok 4 - popen_delete
-	*** popen_kill: done ***
-ok 3 - subtests
-	*** main_f: done ***