internal/mmap: use syscall.Mmap on solaris only with go1.20+

syscall.Mmap,Munmap are available on solaris only after go1.20

Fixes golang/go#60968

Change-Id: I39452dfffef16a55af69c328341e3deb3053dd8d
Reviewed-on: https://go-review.googlesource.com/c/telemetry/+/505715
Run-TryBot: Hyang-Ah Hana Kim <[email protected]>
Reviewed-by: Jamal Carvalho <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: hyangah

internal/mmap/mmap_other.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (js && wasm) || wasip1 || plan9
+//go:build (js && wasm) || wasip1 || plan9 || (solaris && !go1.20)
 
 package mmap
 

internal/mmap/mmap_unix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build unix
+//go:build unix && (!solaris || go1.20)
 
 package mmap