check application-specific make_force_build values in config.exs

[cocoa-xu]

This PR allows users to set application-specific make_force_build values in config.exs for the following reasons:

1. when the precompiled artefacts are linked with a higher version of glibc. In such case, the shared library will fail to load even if the target triplet matches.

   iex> Mix.install([{:exqlite, "~> 0.13.4"}])
   iex> {:ok, conn} = Exqlite.Sqlite3.open(":memory:")
   ** (UndefinedFunctionError) function Exqlite.Sqlite3NIF.open/2 is undefined (module Exqlite.Sqlite3NIF is not available)
       (exqlite 0.13.4) Exqlite.Sqlite3NIF.open(':memory:', 6)
       iex:1: (file)
   iex>
   16:47:22.044 [warning] The on_load function for module Elixir.Exqlite.Sqlite3NIF returned:
   {:error,
    {:load_failed,
     'Failed to load NIF library: \'/lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.28\' not found (required by 
   /root/myapp/_build/dev/lib/exqlite/priv/sqlite3_nif.so)\''}}

2. When the user wants to compile a NIF library natively on the host (to get better optimization, etc).

With this patch applied, users can set make_force_build option for each app. For example, to opt out of using precompiled artefacts of exqlite, they can have the following settings in their config/config.exs:

import Config

config :exqlite, make_force_build: true

Related issue: elixir-sqlite/exqlite#238

[warmwaffles]

Awesome! @cocoa-xu could you submit a PR about that configuration option?

[cocoa-xu]

Awesome! @cocoa-xu could you submit a PR about that configuration option?

Sure! In a minute!

[josevalim]

I would prefer to not assume we can hijack the application environment. I think instead sqlite3 could do make_force_build: Application.get_env(:exsqlite3, :force_build, false) in its mix.exs. WDYT?

[cocoa-xu]

I would prefer to not assume we can hijack the application environment. I think instead sqlite3 could do make_force_build: Application.get_env(:exsqlite3, :force_build, false) in its mix.exs. WDYT?

I'm okay with either one. But I agree that it seems easier to do make_force_build: Application.get_env(:exqlite, :force_build, false) in its mix.exs.

[josevalim]

So let's go that route and, if for some reason it does not work, let me know!

[warmwaffles]

@josevalim are you suggesting that goes in the project/0 function call in mix.exs like this elixir-sqlite/exqlite#241 ?

[josevalim]

Correct!

[warmwaffles]

Thanks!