Ensure eclipse classpath excludes binary output folders

Update `EclipseConventions` so that classpath `whenMerged` changes
are applied via `JavaBasePlugin`. Without this change, the `whenMerged`
item is added, but then`EclipsePlugin.configureEclipseClasspath` is
called from a `project.getPlugins().withType(JavaBasePlugin.class, ...`
call. Using a nested call appears to fix the issue, probably because
it now runs after `configureEclipseClasspath`.

Closes gh-46319

buildSrc/src/main/java/org/springframework/boot/build/EclipseConventions.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.build;
 
 import org.gradle.api.Project;
+import org.gradle.api.plugins.JavaBasePlugin;
 import org.gradle.plugins.ide.api.XmlFileContentMerger;
 import org.gradle.plugins.ide.eclipse.EclipsePlugin;
 import org.gradle.plugins.ide.eclipse.model.Classpath;
@@ -34,10 +35,12 @@ import org.gradle.plugins.ide.eclipse.model.Library;
 class EclipseConventions {
 
 	void apply(Project project) {
-		project.getPlugins().withType(EclipsePlugin.class, (eclipse) -> {
-			EclipseModel eclipseModel = project.getExtensions().getByType(EclipseModel.class);
-			eclipseModel.classpath(this::configureClasspath);
-		});
+		project.getPlugins()
+			.withType(EclipsePlugin.class,
+					(eclipse) -> project.getPlugins().withType(JavaBasePlugin.class, (javaBase) -> {
+						EclipseModel eclipseModel = project.getExtensions().getByType(EclipseModel.class);
+						eclipseModel.classpath(this::configureClasspath);
+					}));
 	}
 
 	private void configureClasspath(EclipseClasspath classpath) {