build: Use Qt top-level build facilities

Summary:

build: Use Qt top-level build facilities

build, qt: Add linguist_tools list

build, qt: Drop lrelease dependency patch

It is no longer required after switching to Qt top-level build.

build, qt: Drop translations.pro hack

It is no longer required after switching to Qt top-level build.

build, qt: Force bootstrap while building linguist tools

Qt lrelease tool depends on the xml module. This change guarantees that
it is always available after being bootstrapped.

build, qt: Fix wrong cross-compiling detection on macOS

This is a backport of core#20641

Test Plan:
cd depends && HOST=x86_64-linux-gnu make qt
Run gitian builds

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13872