Disable Display.post tests if not running on GitHub actions

This is really just a workaround but:

Fixes #2571

Author: jonahgraham

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_custom_StyledText.java

@@ -25,6 +25,7 @@
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.junit.Assume.assumeFalse;
+import static org.junit.Assume.assumeTrue;
 
 import java.util.ArrayList;
 import java.util.Random;
@@ -79,6 +80,7 @@
 import org.junit.Assume;
 import org.junit.Before;
 import org.junit.Test;
+import org.junit.jupiter.api.condition.EnabledIfEnvironmentVariable;
 
 /**
  * Automated Test Suite for class org.eclipse.swt.custom.StyledText
@@ -5897,7 +5899,11 @@ public void test_arrowDownKeepsPositionAfterNewLine() {
  * Bug 565164 - SWT.BS event no longer working
  */
 @Test
+@EnabledIfEnvironmentVariable(named = "GITHUB_ACTIONS", matches = "true", disabledReason = "Display.post tests only run successfully on GitHub actions - see https://github.com/eclipse-platform/eclipse.platform.swt/issues/2571")
 public void test_backspaceAndDelete() throws InterruptedException {
+	assumeTrue(
+			"Display.post tests only run successfully on GitHub actions - see https://github.com/eclipse-platform/eclipse.platform.swt/issues/2571",
+			Boolean.parseBoolean(System.getenv("GITHUB_ACTIONS")));
 	shell.open();
 	text.setSize(10, 50);
 	// The display.post needs to successfully obtain the focused window (at least on GTK3)

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_widgets_Display.java

@@ -48,6 +48,7 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInfo;
 import org.junit.jupiter.api.condition.DisabledOnOs;
+import org.junit.jupiter.api.condition.EnabledIfEnvironmentVariable;
 
 /**
  * Automated Test Suite for class org.eclipse.swt.widgets.Display
@@ -1064,6 +1065,7 @@ public void test_mapLorg_eclipse_swt_widgets_ControlLorg_eclipse_swt_widgets_Con
 }
 
 @Test
+@EnabledIfEnvironmentVariable(named = "GITHUB_ACTIONS", matches = "true", disabledReason = "Display.post tests only run successfully on GitHub actions - see https://github.com/eclipse-platform/eclipse.platform.swt/issues/2571")
 public void test_postLorg_eclipse_swt_widgets_Event() {
 	final int KEYCODE = SWT.SHIFT;
 

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_widgets_Text.java

@@ -17,6 +17,7 @@
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
 
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.events.ModifyListener;
@@ -1551,6 +1552,9 @@ private void doSegmentsTest (boolean isListening) {
  */
 @Test
 public void test_backspaceAndDelete() throws InterruptedException {
+	assumeTrue(
+			"Display.post tests only run successfully on GitHub actions - see https://github.com/eclipse-platform/eclipse.platform.swt/issues/2571",
+			Boolean.parseBoolean(System.getenv("GITHUB_ACTIONS")));
 	shell.open();
 	text.setSize(10, 50);
 	// The display.post needs to successfully obtain the focused window (at least on GTK3)