bring back partial support for 1.12 #411

Job	Run time
static analysis (Elixir 1.15.x \| Erlang/OTP 26.x)	1m 7s
mix test windows (Elixir 1.12.x \| Erlang/OTP 22.x)	1m 8s
mix test windows (Elixir 1.12.x \| Erlang/OTP 23.x)	1m 23s
mix test (Elixir 1.12.x \| Erlang/OTP 22.x)	28s
mix test windows (Elixir 1.12.x \| Erlang/OTP 24.x)	1m 24s
mix test (Elixir 1.12.x \| Erlang/OTP 23.x)	17s
mix test windows (Elixir 1.13.x \| Erlang/OTP 22.x)	2m 17s
mix test (Elixir 1.12.x \| Erlang/OTP 24.x)	16s
mix test windows (Elixir 1.13.x \| Erlang/OTP 23.x)	1m 55s
mix test (Elixir 1.13.x \| Erlang/OTP 22.x)	57s
mix test windows (Elixir 1.13.x \| Erlang/OTP 24.x)	1m 50s
mix test (Elixir 1.13.x \| Erlang/OTP 23.x)	47s
mix test windows (Elixir 1.13.x \| Erlang/OTP 25.x)	1m 51s
mix test (Elixir 1.13.x \| Erlang/OTP 24.x)	41s
mix test windows (Elixir 1.14.x \| Erlang/OTP 23.x)	2m 13s
mix test (Elixir 1.13.x \| Erlang/OTP 25.x)	1m 0s
mix test windows (Elixir 1.14.x \| Erlang/OTP 24.x)	1m 57s
mix test (Elixir 1.14.x \| Erlang/OTP 23.x)	1m 20s
mix test windows (Elixir 1.14.x \| Erlang/OTP 25.x)	2m 13s
mix test (Elixir 1.14.x \| Erlang/OTP 24.x)	1m 10s
mix test windows (Elixir 1.14.x \| Erlang/OTP 26.x)	2m 2s
mix test (Elixir 1.14.x \| Erlang/OTP 25.x)	38s
mix test windows (Elixir 1.15.x \| Erlang/OTP 24.x)	2m 8s
mix test (Elixir 1.14.x \| Erlang/OTP 26.x)	1m 6s
mix test windows (Elixir 1.15.x \| Erlang/OTP 25.x)	2m 3s
mix test (Elixir 1.15.x \| Erlang/OTP 24.x)	1m 3s
mix test windows (Elixir 1.15.x \| Erlang/OTP 26.x)	1m 49s
mix test (Elixir 1.15.x \| Erlang/OTP 25.x)	54s
mix test (Elixir 1.15.x \| Erlang/OTP 26.x)	53s
	38m 50s

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