Embed AppIcon.png within binary

[fkorotkov]

I got the following error when tried to install tart binary in /usr/local/bin/tart and ran tart run monterey-base:

$: tart run monterey-base
tart/resource_bundle_accessor.swift:11: Fatal error: could not load resource bundle: from /usr/local/bin/Tart_tart.bundle or /private/var/folders/7v/mm9qgx011bs6q4k8mmj_jrt40000gn/T/cirrus-build/.build/arm64-apple-macosx/debug/Tart_tart.bundle

It appeared that Swift Package Manager doesn't embed resources within a binary. I'm still a noob with swift so it was a discovery for me. Since we are planning to distribute Tart as a single binary via a Homebrew formula we need somhow embed the only icon we need within the binary.

I didn't find a better way then just embed the icon data as a base64 string. I've tried to implement a Plugin that can do such embedding during a build phase but seems the Swift Plugins are not yet mature to allow such functionality. So I decidede to implement this hack since we only have one icon to embed.

PS I've also put the tart.entitelements file outside of the source root since there was a warning:

'cirrus-build': warning: found 1 file(s) which are unhandled; explicitly declare them as resources or exclude from the target
    /private/var/folders/7v/mm9qgx011bs6q4k8mmj_jrt40000gn/T/cirrus-build/Sources/tart/tart.entitlements