Skip linux_bionic by default in the build tests.

It doesn't work in the build test - it's for use in Soong-only builds.
Specifically Soong fails for dependencies on libLLVM_android, which is
disabled in those builds. To work it needs either
FORCE_BUILD_LLVM_COMPONENTS=true or
SOONG_ALLOW_MISSING_DEPENDENCIES=true to be passed to the build.

Test: build_test presubmits
Bug: 31559095
Bug: 229123823
Change-Id: I7a2b231816012de01472b478e7a98e2b0e929363
diff --git a/build_test.bash b/build_test.bash
index 1dc6660..8b91e2c 100755
--- a/build_test.bash
+++ b/build_test.bash
@@ -25,7 +25,8 @@
 
 # Products that are broken or otherwise don't work with multiproduct_kati
 SKIPPED_PRODUCTS=(
-    # Both of these products are for soong-only builds, and will fail the kati stage.
+    # These products are for soong-only builds, and will fail the kati stage.
+    linux_bionic
     mainline_sdk
     ndk
 )