I have this error on armv6/7:
```
error: couldn't load codegen backend "/usr/ports/lang/rust/work/rustc-1.37.0-src/build/armv6-unknown-freebsd/stage1/lib/rustlib/armv6-unknown-freebsd/codegen-backends/librustc_codegen_llvm-llvm.so": "/usr/ports/lang/rust/work/rustc-1.37.0-src/build/armv6-unknown-freebsd/stage1/lib/rustlib/armv6-unknown-freebsd/codegen-backends/librustc_codegen_llvm-llvm.so: Undefined symbol \"__clear_cache\""
```
__clear_cache is implemented in compiler-rt and was dropped upstream with this commit:
[[ https://github.com/rust-lang-nursery/compiler-builtins/commit/aa41e0d25fcb2b11b9b5c269846dd70547f2a787 | Remove `compiler-rt` submodule from this repository ]]
Is it possible to bring back compiler-rt? Should I try to just import clear_cache.c?