Fixes for gtests in eng-prod

Bug: 147817558
Test: art/art-host-gtest on forrest
Change-Id: I0ecfbc81fe6998d4c8c69ce6fbeb35bdd5908b55
diff --git a/build/art.go b/build/art.go
index af2a5de..6e9e9fd 100644
--- a/build/art.go
+++ b/build/art.go
@@ -17,6 +17,7 @@
 import (
 	"fmt"
 	"log"
+	"path/filepath"
 	"strings"
 	"sync"
 
@@ -25,6 +26,7 @@
 	"android/soong/android"
 	"android/soong/apex"
 	"android/soong/cc"
+	"android/soong/cc/config"
 )
 
 var supportedArches = []string{"arm", "arm64", "x86", "x86_64"}
@@ -167,6 +169,9 @@
 		cflags = append(cflags, "-DART_ENABLE_ADDRESS_SANITIZER=1")
 	}
 
+	clang_path := filepath.Join(config.ClangDefaultBase, ctx.Config().PrebuiltOS(), config.ClangDefaultVersion)
+	cflags = append(cflags, "-DART_CLANG_PATH=\""+clang_path+"\"")
+
 	return cflags
 }