runtime: TestSpuriousWakeupsNeverHangSemasleep failures due to uncaught SIGIO

[bcmills]

--- FAIL: TestSpuriousWakeupsNeverHangSemasleep (0.22s)
    semasleep_test.go:57: The program returned but unfortunately with an error: signal: pollable Event
FAIL
FAIL	runtime	126.911s

greplogs --dashboard -md -l -e '(?m)FAIL: TestSpuriousWakeupsNeverHangSemasleep .*\n.*with an error: signal:'

2021-11-11T19:41:06-f1935c5/solaris-amd64-oraclerel
2021-09-30T16:34:25-d4aed7e/solaris-amd64-oraclerel
2021-08-25T19:45:20-6cf1d5d/linux-riscv64-jsing
2021-07-02T20:11:05-287c5e8/solaris-amd64-oraclerel
2021-06-30T17:58:50-7d0e9e6/solaris-amd64-oraclerel
2021-06-18T23:57:09-86743e7/solaris-amd64-oraclerel
2021-04-19T21:27:43-e97d8eb/linux-riscv64-jsing
2020-11-05T22:14:40-8e5778e/linux-riscv64-jsing
2020-08-18T08:47:48-4149493/solaris-amd64-oraclerel
2020-02-07T18:07:47-cb16d26/solaris-amd64-oraclerel

[gopherbot]

Change https://golang.org/cl/366255 mentions this issue: runtime: in TestSpuriousWakeupsNeverHangSemasleep, wait for the runtime to register handlers