product variables are consumed via soong injection Currently the list of product variables and whether they are arch-variant is hard-coded. Instead, we can generate this data from the Soong Product_variables struct and use soong_injection to consume it in Bazel. Bug: 209801976 Test: m bp2build && run build/bazel/ci/mixed_libc.sh Change-Id: I7efc71cd8a04c189d0c8e2963d4be915382db807