If a signal is sent to t.signal before the panic is triggered,
a panicking test may end up with "warning: no tests to run" because
the tRunner that invokes the test in t.Run calls runtime.Goexit on
panic, which causes the panicking test not be recorded in runTests.
Send the signal if and only if there is no panic.
Fixes #41479
Change-Id: I812f1303bfe02c443a1902732e68d21620d6672e
Reviewed-on: https://go-review.googlesource.com/c/go/+/256098
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Trust: Emmanuel Odeke <emm.odeke@gmail.com>
Trust: Bryan C. Mills <bcmills@google.com>