Enable compilation for specific target

[xofyarg]

Description

By exposing the target information through CompilerConfig,
compiler(only LLVM at the moment) could create a machine with
different CPU feature flags other than current host, which makes it
capable to "cross compile" to some degree.

Update #959

Review

• Add a short description of the the change to the CHANGELOG.md file

[Hywan]

Thanks for the PR. It looks interesting. Maybe @nlewycky can provide me valuable insights.

[syrusakbary]

bors r+

[bors]

Build failed

• wasmerio.wasmer

[syrusakbary]

@xofyarg it seems src/bin/kwasmd.rs CompilerConfig needs to be updated with the new fields (tests are failing).

From tests:

error[E0063]: missing fields `cpu_features`, `cpu_name`, `triple` in initializer of `wasmer_runtime_core::backend::CompilerConfig`
  --> src/bin/kwasmd.rs:60:9
   |
60 |         CompilerConfig {
   |         ^^^^^^^^^^^^^^ missing `cpu_features`, `cpu_name`, `triple`

Once that's addressed it should be good to merge!

[xofyarg]

PR updated.

[MarkMcCaskey]

@xofyarg Can you add a brief explanation to the unimplemented!s? Even just like clif::func_name is fine. It makes debugging these things a lot easier.

I'll ship it as soon that's updated!

[xofyarg]

Brief explanation added and rebased.

[MarkMcCaskey]

Perfect -- thank you!

[MarkMcCaskey]

bors r+

[bors]

Build succeeded

• wasmerio.wasmer