Handle input/output paths from `PBXShellScriptBuildPhase`

[lacasseio]

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As a follow-up to https://github.com/nokeedev/gradle-native/issues/661, we need to handle the input/output paths of PBXShellScriptBuildPhase. Those paths can contain build settings references which means we need to resolve them before we can resolve the paths.

Note that the input/output paths could refer to intermediate files which should not be included in the task up-to-date check. We can make some educated guesses, but we won't be able to completely detect all inputs/outputs without some user intervention. In those cases, we absolutely need to warn the user. We could disable up-to-date checks until the user validates we correctly detected the inputs/outputs. Incorrectly detecting up-to-dateness is quite damaging in terms of the trust.