unix: update code generation for illumos

Since illumos now has a separate syscall_illumos.go along with
syscall_solaris{_amd64}.go, code generation process requires some
update. This commit adds a --illumos for mksyscall_solaris.go, and adds
handling for $GOOS=illumos.

Author: Araragi Hokuto

unix/mkall.sh

@@ -190,6 +190,12 @@ solaris_amd64)
 	mksysnum=
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
+illumos_amd64)
+        mksyscall="go run mksyscall_solaris.go"
+	mkerrors=
+	mksysnum=
+	mktypes=
+	;;
 *)
 	echo 'unrecognized $GOOS_$GOARCH: ' "$GOOSARCH" 1>&2
 	exit 1
@@ -217,6 +223,11 @@ esac
 				echo "$mksyscall -tags $GOOS,$GOARCH,go1.12 $syscall_goos $GOOSARCH_in |gofmt >zsyscall_$GOOSARCH.go";
 				# 1.13 and later, syscalls via libSystem (including syscallPtr)
 				echo "$mksyscall -tags $GOOS,$GOARCH,go1.13 syscall_darwin.1_13.go |gofmt >zsyscall_$GOOSARCH.1_13.go";
+			elif [ "$GOOS" == "illumos" ]; then
+			        # illumos code generation requires a --illumos switch
+			        echo "$mksyscall -illumos -tags illumos,$GOARCH syscall_illumos.go |gofmt > zsyscall_illumos_$GOARCH.go";
+			        # illumos implies solaris, so solaris code generation is also required
+				echo "$mksyscall -tags solaris,$GOARCH syscall_solaris.go syscall_solaris_$GOARCH.go |gofmt >zsyscall_solaris_$GOARCH.go";
 			else
 				echo "$mksyscall -tags $GOOS,$GOARCH $syscall_goos $GOOSARCH_in |gofmt >zsyscall_$GOOSARCH.go";
 			fi

unix/mksyscall_solaris.go

@@ -35,6 +35,7 @@ var (
 	b32  = flag.Bool("b32", false, "32bit big-endian")
 	l32  = flag.Bool("l32", false, "32bit little-endian")
 	tags = flag.String("tags", "", "build tags")
+	illumos = flag.Bool("illumos", false, "illumos specific code generation")
 )
 
 // cmdLine returns this programs's commandline arguments
@@ -306,8 +307,12 @@ func main() {
 	imp := ""
 	if pack != "unix" {
 		imp = "import \"golang.org/x/sys/unix\"\n"
+	}
 
+	if !*illumos {
+		imp += "import \"syscall\"\n"
 	}
+	
 	vardecls := "\t" + strings.Join(vars, ",\n\t")
 	vardecls += " syscallFunc"
 	fmt.Printf(srcTemplate, cmdLine(), buildTags(), pack, imp, dynimports, linknames, vardecls, text)
@@ -320,10 +325,7 @@ const srcTemplate = `// %s
 
 package %s
 
-import (
-	"syscall"
-	"unsafe"
-)
+import "unsafe"
 %s
 %s
 %s