ci: build msan's libc++ with _LIBCPP_ABI_BOUNDED_*

For the task `MSan, depends (Cirrus CI)` we build a custom libc++ for
which we already use `-DLIBCXX_HARDENING_MODE=debug`. Compile it also
with `_LIBCPP_ABI_BOUNDED_*` to enable further checks.

Docs at: https://libcxx.llvm.org/Hardening.html#abi-options

ci/test/01_base_install.sh

@@ -74,6 +74,7 @@ if [[ ${USE_MEMORY_SANITIZER} == "true" ]]; then
     -DLLVM_TARGETS_TO_BUILD=Native \
     -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF \
     -DLIBCXXABI_USE_LLVM_UNWINDER=OFF \
+    -DLIBCXX_ABI_DEFINES="_LIBCPP_ABI_BOUNDED_ITERATORS;_LIBCPP_ABI_BOUNDED_ITERATORS_IN_STD_ARRAY;_LIBCPP_ABI_BOUNDED_ITERATORS_IN_STRING;_LIBCPP_ABI_BOUNDED_ITERATORS_IN_VECTOR;_LIBCPP_ABI_BOUNDED_UNIQUE_PTR" \
     -DLIBCXX_HARDENING_MODE=debug \
     -S /msan/llvm-project/runtimes