LLVM_ENABLE_RUNTIMES for cross compilation

I cannot find documentation about -DLLVM_ENABLE_RUNTIMES=compiler-rt for cross compilation. For example, if I want to build mips64el compiler-rt on an x86-64 host and build some sanitizer tests (ninja check-sanitizer), what CMake command should I use?

I have installed g++-mips64el-linux-gnuabi64 and qemu-user-static on Debian. Many programs run correctly if I use clang --target=mips64el-linux-gnuabi64 -Wl,--dynamic-linker=/usr/mips64el-linux-gnuabi64/lib/ld-2.33.so -Wl,-rpath=/usr/mips64el-linux-gnuabi64/lib.

Folks who know the answer may update llvm/docs/HowToCrossCompileLLVM.rst and llvm/docs/HowToCrossCompileBuiltinsOnArm.rst, and Building libc++ — libc++ documentation

When I did this for our setup I basically copied the Fuchsia CMake cache and adapted the runtime bits of that.

But yeah it should be documented better.