[ci] Create a release after build

[swift-kim]

Fixes #230.

• Add the release job. The job should be added to the same workflow as the build job in order to use download-artifact.
• Minor cleanups.
  • Support non-bash shell. I found that the Linux build step runs in non-bash shell and generates an error (not detected by GA runner as a failure) since [ci] Remove EFL from the Docker image #247.

    [1/9] CXX obj/flutter/shell/version/version.version.o
    [2/9] STAMP obj/flutter/shell/version/version.stamp
    [3/9] SOLINK ./libflutter_engine.so
    /__w/_temp/60f4062e-3cb9-4b1e-9ef0-7e336789af2d.sh: 24: [[: not found
    

  • Make expressions simple and consistent.

Test: https://github.com/swift-kim/engine/actions/runs/1891287349

[bbrto21]

Test: https://github.com/swift-kim/engine/actions/runs/1891287349

Nice work!

[bbrto21]

LGTM
(How about change this work flow name such as "Build and Release" or something more comprehensive?)

[swift-kim]

How about change this work flow name such as "Build and Release" or something more comprehensive?

@bbrto21 Well, since the release job is not applicable for PR runs, it would be better to keep the current name. I don't have other good options right now.