cmd/go: document 'go run' exit codes

Updated docs that go run does not return the exit code of
the compiled binary.

Fixes #23716

Change-Id: Ib85459974c4c6d2760ddba957ef711628098661f
Reviewed-on: https://go-review.googlesource.com/94795Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/go/alldocs.go

@@ -717,6 +717,8 @@
 // cross-compiled programs when a simulator or other execution method is
 // available.
 //
+// The exit status of Run is not the exit status of the compiled binary.
+//
 // For more about build flags, see 'go help build'.
 //
 // See also: go build.

src/cmd/go/internal/run/run.go

@@ -34,6 +34,8 @@ for example 'go_nacl_386_exec a.out arguments...'. This allows execution of
 cross-compiled programs when a simulator or other execution method is
 available.
 
+The exit status of Run is not the exit status of the compiled binary.
+
 For more about build flags, see 'go help build'.
 
 See also: go build.