Build Go tools for arm

Test: prebuilts/build-tools/build-prebuilts.sh
Change-Id: I915be7bb7451f27fcd4beba5e6487da7a01639a6
diff --git a/ui/build/path.go b/ui/build/path.go
index cc1d7e9..b92d799 100644
--- a/ui/build/path.go
+++ b/ui/build/path.go
@@ -20,7 +20,6 @@
 	"os"
 	"os/exec"
 	"path/filepath"
-	"runtime"
 	"strings"
 
 	"github.com/google/blueprint/microfactory"
@@ -122,7 +121,7 @@
 	myPath, _ = filepath.Abs(myPath)
 
 	// Set up the checked-in prebuilts path directory for the current host OS.
-	prebuiltsPath, _ := filepath.Abs("prebuilts/build-tools/path/" + runtime.GOOS + "-x86")
+	prebuiltsPath, _ := filepath.Abs("prebuilts/build-tools/path/" + config.PrebuiltOS())
 	myPath = prebuiltsPath + string(os.PathListSeparator) + myPath
 
 	// Set $PATH to be the directories containing the host tool symlinks, and
@@ -258,7 +257,7 @@
 
 	// We put some prebuilts in $PATH, since it's infeasible to add dependencies
 	// for all of them.
-	prebuiltsPath, _ := filepath.Abs("prebuilts/build-tools/path/" + runtime.GOOS + "-x86")
+	prebuiltsPath, _ := filepath.Abs("prebuilts/build-tools/path/" + config.PrebuiltOS())
 	myPath = prebuiltsPath + string(os.PathListSeparator) + myPath
 
 	// Replace the $PATH variable with the path_interposer symlinks, and