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/config/config.go

@@ -15,13 +15,13 @@ import (
 	"net"
 	"net/url"
 	"os"
-	"runtime"
 	"sort"
 	"strconv"
 	"strings"
 
 	"github.com/pkg/errors"
 
+	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/protocol"
 	"github.com/syncthing/syncthing/lib/util"
@@ -549,7 +549,7 @@ loop:
 }
 
 func cleanSymlinks(filesystem fs.Filesystem, dir string) {
-	if runtime.GOOS == "windows" {
+	if build.IsWindows {
 		// We don't do symlinks on Windows. Additionally, there may
 		// be things that look like symlinks that are not, which we
 		// should leave alone. Deduplicated files, for example.

lib/config/config_test.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/d4l3k/messagediff"
 
+	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/events"
 	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/protocol"
@@ -445,7 +446,7 @@ func TestVersioningConfig(t *testing.T) {
 }
 
 func TestIssue1262(t *testing.T) {
-	if runtime.GOOS != "windows" {
+	if !build.IsWindows {
 		t.Skipf("path gets converted to absolute as part of the filesystem initialization on linux")
 	}
 
@@ -538,7 +539,7 @@ func TestFolderCheckPath(t *testing.T) {
 			path: "link",
 			err:  nil,
 		})
-	} else if runtime.GOOS != "windows" {
+	} else if !build.IsWindows {
 		t.Log("running without symlink check")
 		t.Fatal(err)
 	}
@@ -593,7 +594,7 @@ func TestNewSaveLoad(t *testing.T) {
 }
 
 func TestWindowsLineEndings(t *testing.T) {
-	if runtime.GOOS != "windows" {
+	if !build.IsWindows {
 		t.Skip("Windows specific")
 	}
 

lib/config/folderconfiguration.go

@@ -9,13 +9,13 @@ package config
 import (
 	"errors"
 	"fmt"
-	"runtime"
 	"sort"
 	"strings"
 	"time"
 
 	"github.com/shirou/gopsutil/v3/disk"
 
+	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/db"
 	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/protocol"
@@ -64,7 +64,7 @@ func (f FolderConfiguration) Filesystem(fset *db.FileSet) fs.Filesystem {
 
 func (f FolderConfiguration) ModTimeWindow() time.Duration {
 	dur := time.Duration(f.RawModTimeWindowS) * time.Second
-	if f.RawModTimeWindowS < 1 && runtime.GOOS == "android" {
+	if f.RawModTimeWindowS < 1 && build.IsAndroid {
 		if usage, err := disk.Usage(f.Filesystem(nil).URI()); err != nil {
 			dur = 2 * time.Second
 			l.Debugf(`Detecting FS at "%v" on android: Setting mtime window to 2s: err == "%v"`, f.Path, err)
@@ -90,7 +90,7 @@ func (f *FolderConfiguration) CreateMarker() error {
 	}
 
 	permBits := fs.FileMode(0777)
-	if runtime.GOOS == "windows" {
+	if build.IsWindows {
 		// Windows has no umask so we must chose a safer set of bits to
 		// begin with.
 		permBits = 0700
@@ -145,7 +145,7 @@ func (f *FolderConfiguration) CreateRoot() (err error) {
 	// Directory permission bits. Will be filtered down to something
 	// sane by umask on Unixes.
 	permBits := fs.FileMode(0777)
-	if runtime.GOOS == "windows" {
+	if build.IsWindows {
 		// Windows has no umask so we must chose a safer set of bits to
 		// begin with.
 		permBits = 0700

lib/config/migrations.go

@@ -11,11 +11,11 @@ import (
 	"os"
 	"path"
 	"path/filepath"
-	"runtime"
 	"sort"
 	"strings"
 	"sync"
 
+	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/upgrade"
 	"github.com/syncthing/syncthing/lib/util"
@@ -189,7 +189,7 @@ func migrateToConfigV24(cfg *Configuration) {
 
 func migrateToConfigV23(cfg *Configuration) {
 	permBits := fs.FileMode(0777)
-	if runtime.GOOS == "windows" {
+	if build.IsWindows {
 		// Windows has no umask so we must chose a safer set of bits to
 		// begin with.
 		permBits = 0700