Revert "Fixup migration setting to be thread safe"

This reverts commit 6f07422.

app/meta.go

@@ -2,7 +2,6 @@ package app
 
 import (
 	"fyne.io/fyne/v2"
-	"fyne.io/fyne/v2/internal/build"
 )
 
 var meta = fyne.AppMetadata{
@@ -25,8 +24,6 @@ func SetMetadata(m fyne.AppMetadata) {
 	}
 	if meta.Migrations == nil {
 		meta.Migrations = map[string]bool{}
-	} else {
-		setupMigrations(m.Migrations)
 	}
 }
 
@@ -37,9 +34,3 @@ func (a *fyneApp) Metadata() fyne.AppMetadata {
 
 	return meta
 }
-
-func setupMigrations(data map[string]bool) {
-	if done, ok := data["fyneDo"]; ok && done {
-		build.DisableThreadChecks = true
-	}
-}

app/meta_development.go

@@ -44,7 +44,6 @@ func checkLocalMetadata() {
 	meta.Release = false
 	meta.Custom = data.Development
 	meta.Migrations = data.Migrations
-	setupMigrations(data.Migrations)
 }
 
 func getProjectPath() string {

internal/async/goroutine.go

@@ -30,7 +30,7 @@ func IsMainGoroutine() bool {
 //
 // This will be removed later and should never be public
 func EnsureNotMain(fn func()) {
-	if build.DisableThreadChecks || !build.HasHints || !IsMainGoroutine() {
+	if build.MigratedToFyneDo() || !build.HasHints || !IsMainGoroutine() {
 		fn()
 		return
 	}
@@ -47,7 +47,7 @@ func EnsureNotMain(fn func()) {
 //
 // This will be removed later and should never be public
 func EnsureMain(fn func()) {
-	if build.DisableThreadChecks || !build.HasHints || IsMainGoroutine() {
+	if build.MigratedToFyneDo() || !build.HasHints || IsMainGoroutine() {
 		fn()
 		return
 	}

internal/build/build.go

@@ -1,2 +1,16 @@
 // Package build contains information about they type of build currently running.
 package build
+
+import "fyne.io/fyne/v2"
+
+func MigratedToFyneDo() bool {
+	if DisableThreadChecks {
+		return true
+	}
+
+	v, ok := fyne.CurrentApp().Metadata().Migrations["fyneDo"]
+	if ok {
+		return v
+	}
+	return false
+}

internal/build/migrated_fynedo.go

@@ -3,4 +3,4 @@
 package build
 
 // DisableThreadChecks disables the thread safety checks for performance.
-var DisableThreadChecks = true
+const DisableThreadChecks = true

internal/build/migrated_notfynedo.go

@@ -3,4 +3,4 @@
 package build
 
 // DisableThreadChecks set to false enables the thread safety checks for logging of incorrect usage.
-var DisableThreadChecks = false
+const DisableThreadChecks = false