Update the test harness to GN's location for the host's dart_bootstrap.

tools/testing/dart/compiler_configuration.dart

Index: tools/testing/dart/compiler_configuration.dart
diff --git a/tools/testing/dart/compiler_configuration.dart b/tools/testing/dart/compiler_configuration.dart
index b777fb7761ea07123118a9add9a49a0f1103f56e..f78b91653365223534141c353db4be98d26b1a68 100644
--- a/tools/testing/dart/compiler_configuration.dart
+++ b/tools/testing/dart/compiler_configuration.dart
@@ -565,7 +565,12 @@ class PrecompilerCompilerConfiguration extends CompilerConfiguration {
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
-    var exec = "$buildDir/dart_bootstrap";
+    var exec;
+    if (isAndroid && arch == 'arm') {
+      exec = "$buildDir/clang_x86/dart_bootstrap";
+    } else {
+      exec = "$buildDir/dart_bootstrap";
+    }
     var args = new List();
     args.add("--snapshot-kind=app-aot");
     if (useBlobs) {