Both libraries are listed in lib.json and used as transitive dependencies
(libaom via libavif, brotli via freetype/curl) but had no Windows builder,
causing builds to fail with "library [X] is in the lib.json list but not
supported to compile".
libaom: Uses builddir instead of build to avoid collision with the
source tree's build/cmake/ directory. Matches the Unix builder's
AOM_TARGET_CPU=generic setting for portability.
brotli: Standard CMake build with shared libs and tools disabled.
Also adds static-libs-windows entry for libaom in lib.json.
