Fix Ruby installation error on macOS-10.14 on Azure Pipelines
Fix Ruby installation error on macOS-10.14 on Azure Pipelines

```
Installing openssl-1.1.1i...

BUILD FAILED (Mac OS X 10.14.6 using ruby-build 20201225)

Inspect or clean up the working tree at /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/ruby-build.20210119113044.1658.l6ger2
Results logged to /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/ruby-build.20210119113044.1658.log

Last 10 log lines:
gid   |stat|avg speed  |path/URI
======+====+===========+=======================================================
3a3b72|OK  |    96MiB/s|/private/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/ruby-build.20210119113044.1658.l6ger2/openssl-1.1.1i.tar.gz

Status Legend:
(OK):download completed.
/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/ruby-build.20210119113044.1658.l6ger2/openssl-1.1.1i /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/ruby-build.20210119113044.1658.l6ger2 ~/work/1/s
Operating system: x86_64-whatever-build
This system (build) is not supported. See file INSTALL for details.
make: *** No targets specified and no makefile found.  Stop.
rbenv: version `2.6.2' not installed
```

Set SYSTEM env.
https://developercommunity.visualstudio.com/content/problem/602584/openssl-build-error-when-using-pipelines.html

emsk/romajify,emsk/romajify