Clarify API around CBuildConfiguration.getBuildDirectory as @nooverride

Author: jonahgraham

NewAndNoteworthy/CHANGELOG-API.md

@@ -24,6 +24,11 @@ The following classes have been removed or modified in API breaking ways:
   - spelling corrected for methods with Uninitialized in the name
   - setWarnUnused renamed to setWarnUnusedVars and isWarnUnused renamed to isWarnUnusedVars
 
+## org.eclipse.cdt.core.build.CBuildConfiguration.getBuildDirectory() should not be overridden
+
+The `@nooverride` flag was added to `CBuildConfiguration.getBuildDirectory`.
+Extenders should only be overridding `getBuildDirectoryURI` which is part of the `ICBuildConfiguration2` API.
+`getBuildDirectory` is a convenience method to convert URI into Path.
 
 ## API Changes in CDT 11.5.
 

core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/build/CBuildConfiguration.java

@@ -282,6 +282,13 @@ public URI getBuildDirectoryURI() throws CoreException {
 		return getBuildContainer().getLocationURI();
 	}
 
+	/**
+	 * Convenience method to convert getBuildDirectoryURI() to a Path
+	 * <p>
+	 * @apiNote This method used to be overridable, but it leads to unclear semantics for extenders.
+	 * Extenders looking to change the build directory should only override {@link #getBuildDirectoryURI()}
+	 * @nooverride This method is not intended to be re-implemented or extended by clients.
+	 */
 	public Path getBuildDirectory() throws CoreException {
 		return Paths.get(getBuildDirectoryURI());
 	}