Silent instead of displaying error message when a target is unavailable

[cocoa-xu]

This PR makes it silently fallback to compile or ignore when there is no precompiled binary for the current target (i.e., no corresponding entry existing in the checksum.exs) instead of an error message.

Related issue: elixir-sqlite/exqlite#243

[warmwaffles]

This is definitely a nice to have. I believe the ergonomics will lend itself well here. If the precompiled target is not available it should just build the binaries.

[josevalim]

@cocoa-xu can you please try the commit I pushed? I moved the warning inside the first case to pass less info around :)

[cocoa-xu]

@josevalim It works as intended! No error messages and straightly fallbacks to compile. :)

Before (master branch)

$ export TARGET_ARCH=aarch128
$ iex -S mix  
Erlang/OTP 25 [erts-13.1.5] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

==> exqlite
Error happened while installing exqlite from precompiled binary: cannot find download url for current target `"aarch128--"`. Available targets are: [{"x86_64-linux-musl", "2.16"}, {"x86_64-linux-musl", "2.15"}, {"riscv64-linux-musl", "2.16"}, {"riscv64-linux-musl", "2.15"}, {"aarch64-linux-musl", "2.16"}, {"aarch64-linux-musl", "2.15"}].

Attempting to compile exqlite from source...
 CC sqlite3_nif.o
 CC sqlite3.o
 LD sqlite3_nif.so
ld: warning: -undefined dynamic_lookup may not work with chained fixups
Compiling 13 files (.ex)
Generated exqlite app
Interactive Elixir (1.14.3) - press Ctrl+C to exit (type h() ENTER for help)

After

$ export TARGET_ARCH=aarch128
$ iex -S mix
Erlang/OTP 25 [erts-13.1.5] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

==> exqlite
 CC sqlite3_nif.o
 CC sqlite3.o
 LD sqlite3_nif.so
ld: warning: -undefined dynamic_lookup may not work with chained fixups
Compiling 13 files (.ex)
Generated exqlite app
iex(1)>

[josevalim]

💚 💙 💜 💛 ❤️

[josevalim]

0.7.6 out!