The `__future__` we relied on is now, where the 3 specific things are
all included [since Python 3.0](https://docs.python.org/3/library/__future__.html):
* absolute_import
* print_function
* unicode_literals
* division
These import statements are no-ops and are no longer necessary.
In normal cases, adb_clean.py cleaning the temporal directory is a good
idea because all the tests run in a clean state, and previous executions
do not influence the current one.
However, when iterating and running only one or two tests with
utils/run-test, removing all the artifacts and uploading them to the
device can turn each iteration into waiting a couple of minutes. Since
the changes in between tests should only touch a couple of libraries (or
none at all, if the test itself is the modification), avoiding a full
clean is beneficial.
The commit modifies `adb_clean.py` to allow providing the environment
variable `SKIP_ANDROID_CLEAN`, which will simply not execute the script.
Since the introduction of #24146, only the modified
artifacts will be uploaded, and the test iteration can be very fast
(including no time, if there are no changes).
This adds support for running tests for the stdlib built
for Android, both on the host machine and on an Android device.
The Android variant of Swift may be built and tested using
the following `build-script` invocation:
```
$ utils/build-script \
-R \ # Build in ReleaseAssert mode.
-T \ # Run all tests.
--android \ # Build for Android.
--android-deploy-device-path /data/local/tmp \ # Temporary directory on the device where Android tests are run.
--android-ndk ~/android-ndk-r10e \ # Path to an Android NDK.
--android-ndk-version 21 \
--android-icu-uc ~/libicu-android/armeabi-v7a/libicuuc.so \
--android-icu-uc-include ~/libicu-android/armeabi-v7a/icu/source/common \
--android-icu-i18n ~/libicu-android/armeabi-v7a/libicui18n.so \
--android-icu-i18n-include ~/libicu-android/armeabi-v7a/icu/source/i18n/
```
See docs/Testing.rst for more details.
