[release-branch.go1.21] runtime: mark traceEnabled and traceShuttingDown as no:split

This fixes a regression from CL 494181.
The traceEnabled function splits the stack and is being
called by reentersyscall that shouldn't call anything
that splits the stack. Same with traceShuttingDown.

For #61975
Fixes #61987

Change-Id: I5eca0ba74cfa6acb0259e8400b03c2093cd59dd1
GitHub-Last-Rev: 9e55ae9
GitHub-Pull-Request: #61981
Reviewed-on: https://go-review.googlesource.com/c/go/+/519055
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Dmitri Shuralyov <[email protected]>
(cherry picked from commit aa5d483)
Reviewed-on: https://go-review.googlesource.com/c/go/+/519495
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
Run-TryBot: Michael Knyszek <[email protected]>

Author: mauri870

src/runtime/trace.go

@@ -257,11 +257,15 @@ func traceBufPtrOf(b *traceBuf) traceBufPtr {
 }
 
 // traceEnabled returns true if the trace is currently enabled.
+//
+//go:nosplit
 func traceEnabled() bool {
 	return trace.enabled
 }
 
 // traceShuttingDown returns true if the trace is currently shutting down.
+//
+//go:nosplit
 func traceShuttingDown() bool {
 	return trace.shutdown
 }