all: Add build constants for runtime.GOOS comparisons (#8442)

all: Add package runtimeos for runtime.GOOS comparisons

I grew tired of hand written string comparisons. This adds generated
constants for the GOOS values, and predefined Is$OS constants that can
be iffed on. In a couple of places I rewrote trivial switch:es to if:s,
and added Illumos where we checked for Solaris (because they are
effectively the same, and if we're going to target one of them that
would be Illumos...).

lib/ignore/ignore.go

@@ -13,12 +13,12 @@ import (
 	"fmt"
 	"io"
 	"path/filepath"
-	"runtime"
 	"strings"
 	"time"
 
 	"github.com/gobwas/glob"
 
+	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/osutil"
 	"github.com/syncthing/syncthing/lib/sha256"
@@ -35,7 +35,7 @@ const (
 var defaultResult Result = resultInclude
 
 func init() {
-	if runtime.GOOS == "darwin" || runtime.GOOS == "windows" {
+	if build.IsDarwin || build.IsWindows {
 		defaultResult |= resultFoldCase
 	}
 }

lib/ignore/ignore_test.go

@@ -12,11 +12,11 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"runtime"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/osutil"
 )
@@ -210,10 +210,9 @@ func TestCaseSensitivity(t *testing.T) {
 	match := []string{"test"}
 	dontMatch := []string{"foo"}
 
-	switch runtime.GOOS {
-	case "darwin", "windows":
+	if build.IsDarwin || build.IsWindows {
 		match = append(match, "TEST", "Test", "tESt")
-	default:
+	} else {
 		dontMatch = append(dontMatch, "TEST", "Test", "tESt")
 	}
 
@@ -618,7 +617,7 @@ func TestHashOfEmpty(t *testing.T) {
 func TestWindowsPatterns(t *testing.T) {
 	// We should accept patterns as both a/b and a\b and match that against
 	// both kinds of slash as well.
-	if runtime.GOOS != "windows" {
+	if !build.IsWindows {
 		t.Skip("Windows specific test")
 		return
 	}
@@ -643,7 +642,7 @@ func TestWindowsPatterns(t *testing.T) {
 
 func TestAutomaticCaseInsensitivity(t *testing.T) {
 	// We should do case insensitive matching by default on some platforms.
-	if runtime.GOOS != "windows" && runtime.GOOS != "darwin" {
+	if !build.IsWindows && !build.IsDarwin {
 		t.Skip("Windows/Mac specific test")
 		return
 	}
@@ -1205,7 +1204,7 @@ func TestEmptyPatterns(t *testing.T) {
 }
 
 func TestWindowsLineEndings(t *testing.T) {
-	if runtime.GOOS != "windows" {
+	if !build.IsWindows {
 		t.Skip("Windows specific")
 	}