Handle arch/cpu variants in mixed builds

Test: mixed_libc.sh
Change-Id: Ib5084060199b8e1a5955bd51bc3fd793bb83a1eb
diff --git a/tests/lib.sh b/tests/lib.sh
index e6074f8..55f9ab4 100644
--- a/tests/lib.sh
+++ b/tests/lib.sh
@@ -86,6 +86,7 @@
 
   symlink_directory prebuilts/go
   symlink_directory prebuilts/build-tools
+  symlink_directory prebuilts/clang/host
   symlink_directory external/go-cmp
   symlink_directory external/golang-protobuf