Skip mainline_sdk by default in build_test.bash

This product does not work in build_test yet for two reasons:
- it's a soong-only build and kati does not pass
- it requires the FORCE_BUILD_LLVM_COMPONENTS env variable to be set

Bug: 174315599
Test: build_test
Change-Id: I6d1be1a9779028fb6b7504b6853edcd6db71e35a

build_test.bash

@@ -23,6 +23,11 @@
 # evolve as we find interesting things to test or track performance for.
 #
 
+# Products that are broken or otherwise don't work with multiproduct_kati
+SKIPPED_PRODUCTS=(
+    mainline_sdk
+)
+
 # To track how long we took to startup. %N isn't supported on Darwin, but
 # that's detected in the Go code, which skips calculating the startup time.
 export TRACE_BEGIN_SOONG=$(date +%s%N)
@@ -50,4 +55,4 @@ echo "Running Bazel smoke test..."
 echo
 echo "Running Soong test..."
 soong_build_go multiproduct_kati android/soong/cmd/multiproduct_kati
-exec "$(getoutdir)/multiproduct_kati" "$@"
+exec "$(getoutdir)/multiproduct_kati" --skip-products "$(echo "${SKIPPED_PRODUCTS[@]-}" | tr ' ' ',')" "$@"