syscall: add Mmap and Munmap on solaris

They exist on all other Unix ports, define them on GOOS=solaris as well.

Fixes #52875

Change-Id: I7285156b3b48ce12fbcc6d1d88865540a5c51a21
Reviewed-on: https://go-review.googlesource.com/c/go/+/413374
Run-TryBot: Tobias Klauser <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Tobias Klauser <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>

Author: tklauser

src/syscall/mmap_unix_test.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 aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
 
 package syscall_test
 

src/syscall/syscall_solaris.go

@@ -536,6 +536,20 @@ func writelen(fd int, buf *byte, nbuf int) (n int, err error) {
 	return
 }
 
+var mapper = &mmapper{
+	active: make(map[*byte][]byte),
+	mmap:   mmap,
+	munmap: munmap,
+}
+
+func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, err error) {
+	return mapper.Mmap(fd, offset, length, prot, flags)
+}
+
+func Munmap(b []byte) (err error) {
+	return mapper.Munmap(b)
+}
+
 func Utimes(path string, tv []Timeval) error {
 	if len(tv) != 2 {
 		return EINVAL