Bazel: Generate Eclipse classpath

To guess what build system is used, we create now .primary_build_tool
file in the root of the project during the eclipse classpath generation.

Change the working directory for GWT SDM session to be .gwt_work_dir.
The reason for that Bazel doesn't allow to write to bazel-out.

Change-Id: I984068350244ee9d66807e4bc8c6779b34a26bab

gerrit-httpd/src/main/java/com/google/gerrit/httpd/raw/BazelBuild.java

@@ -14,8 +14,11 @@
 
 package com.google.gerrit.httpd.raw;
 
+import static com.google.common.base.MoreObjects.firstNonNull;
+
 import java.io.IOException;
 import java.nio.file.Path;
+import java.util.Properties;
 
 public class BazelBuild extends BuildSystem {
   public BazelBuild(Path sourceRoot) {
@@ -24,7 +27,13 @@ public class BazelBuild extends BuildSystem {
 
   @Override
   protected ProcessBuilder newBuildProcess(Label label) throws IOException {
-    ProcessBuilder proc = new ProcessBuilder("bazel", "build", label.fullName());
+    Properties properties = loadBuildProperties(
+        sourceRoot.resolve(".primary_build_tool"));
+    String buck = firstNonNull(properties.getProperty("bazel"), "bazel");
+    ProcessBuilder proc = new ProcessBuilder(buck, "build", label.fullName());
+    if (properties.containsKey("PATH")) {
+      proc.environment().put("PATH", properties.getProperty("PATH"));
+    }
     return proc;
   }
 

gerrit-httpd/src/main/java/com/google/gerrit/httpd/raw/BuckUtils.java

@@ -17,9 +17,6 @@ package com.google.gerrit.httpd.raw;
 import static com.google.common.base.MoreObjects.firstNonNull;
 
 import java.io.IOException;
-import java.io.InputStream;
-import java.nio.file.Files;
-import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.util.Properties;
 
@@ -30,7 +27,7 @@ class BuckUtils extends BuildSystem {
 
   @Override
   protected ProcessBuilder newBuildProcess(Label label) throws IOException {
-    Properties properties = loadBuckProperties(
+    Properties properties = loadBuildProperties(
         sourceRoot.resolve("buck-out/gen/tools/buck/buck.properties"));
     String buck = firstNonNull(properties.getProperty("buck"), "buck");
     ProcessBuilder proc = new ProcessBuilder(buck, "build", label.fullName());
@@ -40,17 +37,6 @@ class BuckUtils extends BuildSystem {
     return proc;
   }
 
-  private static Properties loadBuckProperties(Path propPath)
-      throws IOException {
-    Properties properties = new Properties();
-    try (InputStream in = Files.newInputStream(propPath)) {
-      properties.load(in);
-    } catch (NoSuchFileException e) {
-      // Ignore; will be run from PATH, with a descriptive error if it fails.
-    }
-    return properties;
-  }
-
   @Override
   public Path targetPath(Label label) {
     return sourceRoot.resolve("buck-out")

gerrit-httpd/src/main/java/com/google/gerrit/httpd/raw/BuildSystem.java

@@ -30,7 +30,10 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.InterruptedIOException;
 import java.io.PrintWriter;
+import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
+import java.util.Properties;
 
 import javax.servlet.http.HttpServletResponse;
 
@@ -46,6 +49,17 @@ public abstract class BuildSystem {
 
   protected abstract ProcessBuilder newBuildProcess(Label l) throws IOException;
 
+  protected static Properties loadBuildProperties(Path propPath)
+      throws IOException {
+    Properties properties = new Properties();
+    try (InputStream in = Files.newInputStream(propPath)) {
+      properties.load(in);
+    } catch (NoSuchFileException e) {
+      // Ignore; will be run from PATH, with a descriptive error if it fails.
+    }
+    return properties;
+  }
+
   // builds the given label.
   public void build(Label label)
       throws IOException, BuildFailureException {