Swift main toolchain missing LLVM realtime sanitizer libraries

[jcavar]

I asked this question on Swift Forums: https://forums.swift.org/t/swift-main-toolchain-missing-llvm-realtime-sanitizer-libraries/82820

But maybe this is a better place. Please redirect me if not.

I downloaded the latest main Swift toolchain (org.swift.62202510171a) and tried to compile a simple C++ program with the new LLVM 20 realtime sanitizer:

xcrun -toolchain "org.swift.62202510171a" clang main.cpp -lstdc++ -fsanitize=realtime

This results in the following error:

ld: file cannot be open()ed, errno=2 path=/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2025-10-17-a.xctoolchain/usr/lib/clang/21/lib/darwin/libclang_rt.rtsan_osx_dynamic.dylib in '/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2025-10-17-a.xctoolchain/usr/lib/clang/21/lib/darwin/libclang_rt.rtsan_osx_dynamic.dylib'

When I look there, rtsan dylib is indeed missing.