log: fix call depth for go1.12 panics

This PR fixes the following test failure on Linux:

```
$ make test IGNORE_GOVERS=1 PKG=./pkg/util/log
--- FAIL: TestCrashReportingPacket (0.20s)
    --- FAIL: TestCrashReportingPacket/#00 (0.00s)
        crash_reporting_packet_test.go:155: expected crash_reporting_packet_test.go:85: boom, got testing.go:865: boom
    --- FAIL: TestCrashReportingPacket/#1 (0.00s)
        crash_reporting_packet_test.go:155: expected crash_reporting_packet_test.go:93: baam, got testing.go:865: baam
FAIL
```

Interestingly this is not quite the same failure noted in #35792, maybe that's
MacOS specific?

Release note: None

pkg/util/log/crash_report_panic_depth_1_11.go

@@ -0,0 +1,29 @@
+// Copyright 2019 The Cockroach Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+// implied. See the License for the specific language governing
+// permissions and limitations under the License.
+
+// +build !go1.12
+
+// This file exists to deal with the fact that the call depth during panics
+// differs before and after go version 1.12. It holds the correct depth for use
+// with go1.11 and prior and carries the appropriate build constraint.
+
+package log
+
+// The call stack here is usually:
+// - ReportPanic
+// - RecoverAndReport
+// - panic.go
+// - panic()
+// so ReportPanic should pop four frames.
+const depthForRecoverAndReportPanic = 4

pkg/util/log/crash_report_panic_depth_1_12.go

@@ -0,0 +1,28 @@
+// Copyright 2019 The Cockroach Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+// implied. See the License for the specific language governing
+// permissions and limitations under the License.
+
+// +build go1.12
+
+// This file exists to deal with the fact that the call depth during panics
+// differs before and after go version 1.12. It holds the correct depth for use
+// with go1.12 and later and carries the appropriate build constraint.
+
+package log
+
+// The call stack here is usually:
+// - ReportPanic
+// - RecoverAndReport
+// - panic()
+// so ReportPanic should pop three frames.
+const depthForRecoverAndReportPanic = 3

pkg/util/log/crash_reporting.go

@@ -91,13 +91,7 @@ var (
 // real stderr a panic has occurred.
 func RecoverAndReportPanic(ctx context.Context, sv *settings.Values) {
 	if r := recover(); r != nil {
-		// The call stack here is usually:
-		// - ReportPanic
-		// - RecoverAndReport
-		// - panic.go
-		// - panic()
-		// so ReportPanic should pop four frames.
-		ReportPanic(ctx, sv, r, 4)
+		ReportPanic(ctx, sv, r, depthForRecoverAndReportPanic)
 		panic(r)
 	}
 }
@@ -106,13 +100,7 @@ func RecoverAndReportPanic(ctx context.Context, sv *settings.Values) {
 // does not re-panic in Release builds.
 func RecoverAndReportNonfatalPanic(ctx context.Context, sv *settings.Values) {
 	if r := recover(); r != nil {
-		// The call stack here is usually:
-		// - ReportPanic
-		// - RecoverAndReport
-		// - panic.go
-		// - panic()
-		// so ReportPanic should pop four frames.
-		ReportPanic(ctx, sv, r, 4)
+		ReportPanic(ctx, sv, r, depthForRecoverAndReportPanic)
 		if !build.IsRelease() || PanicOnAssertions.Get(sv) {
 			panic(r)
 		}