[WIP] ci: Do not cache depends/sources directory #22058

Caching the depends/sources directory does not handle a source file update well, and it causes CI job failure.

See https://cirrus-ci.com/task/5975797421834240:

  CXXLD    qt/bitcoin-qt
  CXXLD    qt/test/test_bitcoin-qt
make[1]: Leaving directory '/tmp/cirrus-ci-build/src'
make -C .. bitcoin_qt_apk
make[1]: Entering directory '/tmp/cirrus-ci-build/src'
tar: ../depends/sources/qtbase-everywhere-src-5.12.11.tar.xz: Not found in archive
tar: Exiting with failure status due to previous errors
tar: ../depends/sources/qtbase-everywhere-src-5.12.11.tar.xz: Not found in archive
tar: Exiting with failure status due to previous errors
tar: ../depends/sources/qtbase-everywhere-src-5.12.11.tar.xz: Not found in archive
tar: Exiting with failure status due to previous errors
mkdir -p qt/android/libs/arm64-v8a
cp /tmp/cirrus-ci-build/depends/SDKs/android/ndk/21.1.6352462/toolchains/llvm/prebuilt/linux-x86_64/bin//../sysroot/usr/lib/aarch64-linux-android/libc++_shared.so qt/android/libs/arm64-v8a
tar xf ../depends/sources/qtbase-everywhere-src-5.12.10.tar.xz ../depends/sources/qtbase-everywhere-src-5.12.11.tar.xz -C qt/android/src/ src/android/jar/src --strip-components=5
tar: ../depends/sources/qtbase-everywhere-src-5.12.11.tar.xz: Not found in archive
tar: src/android/jar/src: Not found in archive
tar: Exiting with failure status due to previous errors
make[1]: *** [Makefile:17975: bitcoin_qt_apk] Error 2
make[1]: Leaving directory '/tmp/cirrus-ci-build/src'
make: *** [Makefile:11: apk] Error 2

Does this mean the sources will be re-downloaded for every CI check, which would be kind of wasteful of resources? Couldn't we make this conditional in some way?

NACK this patch. This is reverting fa52d7d3adc99c0e716628058b4fd083034d27e0

Does this mean the sources will be re-downloaded for every CI check, which would be kind of wasteful of resources?

The depends_sources_cache is used in the only CI job -- ARM64 Android APK [focal]

Couldn't we make this conditional in some way?

I really was trying to find such a way. Another option is to invalidate cache via CI Cirrus web console, but it invalidates all caches.

It shouldn't matter if the thing is downloaded from cirrus cache or from the qt website.

Replacing this with something like this should be just fine:

if android:
 make download qt && make extract qt

If that is too hard to implement, a hacky emergency workaround could be to change the name of the cirrus task to drop the cache.