[Build] Build libcxx on lldb ASAN/UBSAN bots

The preset for ubsan/asan buildbots include the
`buildbot_incremental_base` preset, which builds/runs
tests. But the tests now require libcxx to be built
since #66018

Author: Michael137

utils/build-presets.ini

@@ -535,6 +535,8 @@ mixin-preset=buildbot_incremental_base
 
 build-subdir=buildbot_incremental_lldb_asan_ubsan
 
+# Standalone tests require newly built libcxx
+libcxx
 # Build a sanitized lldb. Don't build a sanitized clang/swift.
 lldb
 lldb-extra-cmake-args=-DLLVM_USE_SANITIZER=Address;Undefined