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

@@ -71,6 +71,13 @@ if [[ ${USE_MEMORY_SANITIZER} == "true" ]]; then
     -DLLVM_USE_SANITIZER=MemoryWithOrigins \
     -DCMAKE_C_COMPILER=clang \
     -DCMAKE_CXX_COMPILER=clang++ \
+    -DCMAKE_CXX_FLAGS="\
+      -D_LIBCPP_ABI_BOUNDED_ITERATORS \
+      -D_LIBCPP_ABI_BOUNDED_ITERATORS_IN_STD_ARRAY \
+      -D_LIBCPP_ABI_BOUNDED_ITERATORS_IN_STRING \
+      -D_LIBCPP_ABI_BOUNDED_ITERATORS_IN_VECTOR \
+      -D_LIBCPP_ABI_BOUNDED_UNIQUE_PTR \
+    " \
     -DLLVM_TARGETS_TO_BUILD=Native \
     -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF \
     -DLIBCXXABI_USE_LLVM_UNWINDER=OFF \