diff --git a/Toolchain/CMake/LLVMRuntimesConfig.cmake b/Toolchain/CMake/LLVMRuntimesConfig.cmake
index dfaa45c2034..b56aff11d20 100644
--- a/Toolchain/CMake/LLVMRuntimesConfig.cmake
+++ b/Toolchain/CMake/LLVMRuntimesConfig.cmake
@@ -60,3 +60,15 @@ set(LIBCXX_ENABLE_STATIC_ABI_LIBRARY ON CACHE BOOL "")
 set(LIBCXX_INCLUDE_BENCHMARKS OFF CACHE BOOL "")
 set(LIBCXXABI_USE_COMPILER_RT ON CACHE BOOL "")
 set(LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
+
+# Hardcode autodetection results for libm, libdl, and libpthread.
+# This keeps us from accidentially detecting those libraries as being present
+# if we build the toolchain with a populated sysroot (which features the
+# compability linker scripts).
+# TODO: Figure out if we can always build against the Stubs directory instead.
+set(LIBCXXABI_HAS_DL_LIB OFF CACHE BOOL "")
+set(LIBCXXABI_HAS_PTHREAD_LIB OFF CACHE BOOL "")
+set(LIBCXX_HAS_M_LIB OFF CACHE BOOL "")
+set(LIBCXX_HAS_PTHREAD_LIB OFF CACHE BOOL "")
+set(LIBUNWIND_HAS_DL_LIB OFF CACHE BOOL "")
+set(LIBUNWIND_HAS_PTHREAD_LIB OFF CACHE BOOL "")