Polyfill SIGCHLD on the New Technology

redbean will now cleanup child processes properly. New accounting
information is available too, such as page faults and memory usage. The
way it works is Cosmopolitan Libc samples the process collection on
entry into read() and poll() to see if SIGCHLD needs to be raised.

This change also fixes an issue with chibicc /tmp cleanup. There was
also a regression in MODE=dbg because STL needed ASAN runtime support.

test/libc/stdio/tmpfile_test.c

@@ -29,7 +29,7 @@ TEST(tmpfile, test) {
   FILE *f;
   mkdir("doge", 0755);
   setenv("TMPDIR", "doge", true);
-  f = tmpfile();
+  ASSERT_NE(NULL, (f = tmpfile()));
   EXPECT_NE(-1, fputc('t', f));
   EXPECT_NE(-1, fflush(f));
   rewind(f);