Add dynamic variable for build directory of active core build config

This will allow us to use that value in external tool launches such
as those used by the Serial Flash launch configuration.

Also removal of the missing src source folder entry in meson.ui.editor.

Change-Id: I1033bdc0c18c9822490a9b8602cef83a42f7262d

build/org.eclipse.cdt.meson.ui.editor/.classpath

@@ -2,6 +2,5 @@
 <classpath>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8"/>
 	<classpathentry kind="con" path="org.eclipse.pde.core.requiredPlugins"/>
-	<classpathentry kind="src" path="src"/>
 	<classpathentry kind="output" path="bin"/>
 </classpath>

core/org.eclipse.cdt.core/plugin.properties

@@ -95,6 +95,7 @@ binaryFileName=Binary File
 cdt_pathentry_var.description=CDT PathEntry variable
 config_name_var.description=The name of the active configuration for the project specified as an argument
 config_description_var.description=The description of the active configuration for the project specified as an argument
+core_build_dir.description=The build directory for the active Core Build configuration for the given project
 
 PDOMProviderName=PDOM Provider
 

core/org.eclipse.cdt.core/plugin.xml

@@ -608,6 +608,12 @@
             resolver="org.eclipse.cdt.internal.core.PathEntryVariableResolver"
             description="%cdt_pathentry_var.description">
       </variable>
+      <variable
+            description="%core_build_dir.description"
+            name="active_core_build_dir"
+            resolver="org.eclipse.cdt.internal.core.build.CBuildDirectoryResolver"
+            supportsArgument="true">
+      </variable>
    </extension>
    <extension
          point="org.eclipse.core.variables.dynamicVariables">

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

@@ -236,6 +236,7 @@ public abstract class CBuildConfiguration extends PlatformObject
 		return buildFolder;
 	}
 
+	@Override
 	public URI getBuildDirectoryURI() throws CoreException {
 		return getBuildContainer().getLocationURI();
 	}

core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/build/ICBuildConfiguration2.java

@@ -10,6 +10,10 @@
  *******************************************************************************/
 package org.eclipse.cdt.core.build;
 
+import java.net.URI;
+
+import org.eclipse.core.runtime.CoreException;
+
 /**
  * @since 6.5
  */
@@ -20,4 +24,9 @@ public interface ICBuildConfiguration2 {
 	 */
 	void setActive();
 
+	/**
+	 * The URI for the directory in which the build is executed.
+	 */
+	URI getBuildDirectoryURI() throws CoreException;
+
 }

core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/core/build/CBuildDirectoryResolver.java

@@ -0,0 +1,55 @@
+/*******************************************************************************
+ * Copyright (c) 2018 QNX Software Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.cdt.internal.core.build;
+
+import java.io.File;
+import java.net.URI;
+
+import org.eclipse.cdt.core.CCorePlugin;
+import org.eclipse.cdt.core.build.ICBuildConfiguration;
+import org.eclipse.cdt.core.build.ICBuildConfiguration2;
+import org.eclipse.cdt.core.build.ICBuildConfigurationManager;
+import org.eclipse.core.resources.IBuildConfiguration;
+import org.eclipse.core.resources.IProject;
+import org.eclipse.core.resources.ResourcesPlugin;
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.variables.IDynamicVariable;
+import org.eclipse.core.variables.IDynamicVariableResolver;
+
+public class CBuildDirectoryResolver implements IDynamicVariableResolver {
+
+	@Override
+	public String resolveValue(IDynamicVariable variable, String argument) throws CoreException {
+		if (argument == null || argument.isEmpty()) {
+			return null;
+		}
+		
+		IProject project = ResourcesPlugin.getWorkspace().getRoot().getProject(argument);
+		if (project == null || !project.exists()) {
+			return null;
+		}
+
+		IBuildConfiguration config = project.getActiveBuildConfig();
+		
+		ICBuildConfigurationManager manager = CCorePlugin.getService(ICBuildConfigurationManager.class);
+		ICBuildConfiguration coreConfig = manager.getBuildConfiguration(config);
+		if (coreConfig == null) {
+			return null;
+		}
+		
+		if (coreConfig instanceof ICBuildConfiguration2) {
+			URI uri = ((ICBuildConfiguration2) coreConfig).getBuildDirectoryURI();
+			if (uri != null) {
+				return new File(uri).getAbsolutePath();
+			}
+		}
+		
+		return null;
+	}
+
+}