go: runtime/trace: TestTraceCPUProfile failures

#!watchflakes
post <- (pkg == "runtime/trace" && test == "TestTraceCPUProfile") || log ~ `--- FAIL: TestTraceCPUProfile`

Issue created automatically to collect these failures.

Example (log):

SIGQUIT: quit
PC=0x86d24 m=7 sigcode=0

trap    0x0
error   0x0
oldmask 0x0
r0      0x2fbadc
r1      0x80
r2      0x0
r3      0x0
...
	/workdir/go/src/runtime/proc.go:1090 +0x98 fp=0x183acfc sp=0x183acdc pc=0x53e88
runtime.stopTheWorldGC({0x1c6ecd, 0xc})
	/workdir/go/src/runtime/proc.go:1137 +0x48 fp=0x183ad10 sp=0x183acfc pc=0x54054
runtime.StopTrace()
	/workdir/go/src/runtime/trace.go:320 +0x24 fp=0x183ad28 sp=0x183ad10 pc=0x74ab8
runtime/trace.Stop()
	/workdir/go/src/runtime/trace/trace.go:148 +0x78 fp=0x183ad44 sp=0x183ad28 pc=0xe697c
runtime/trace_test.TestTraceCPUProfile(0x1c04e10)
	/workdir/go/src/runtime/trace/trace_test.go:621 +0x1a4 fp=0x183af98 sp=0x183ad44 pc=0x1885ec
testing.tRunner(0x1c04e10, 0x1d3994)

— watchflakes