allow use of android string resource id in application label

[xzenodart]

Cargo.toml:

[package.metadata.android]
resources = "res"

[package.metadata.android.application]
label = "@string/app_name"

res/values/strings.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">Localized App Label</string>
</resources>

cargo apk build failed with message:

ERROR: unable to open '/home/user/apkproject/target/debug/apk/@string/app_name-unaligned.apk' as Zip file for writing

[MarijnS95]

Feel free to PR the linked commit for review and merging :)