[CI] Build a Python wheel for aarch64 platform (#6253)

tests/ci_build/conda_env/aarch64_test.yml

@@ -0,0 +1,29 @@
+name: aarch64_test
+channels:
+- conda-forge
+dependencies:
+- python=3.7
+- pip
+- wheel
+- pytest
+- pytest-cov
+- numpy
+- scipy
+- scikit-learn
+- pandas
+- matplotlib
+- dask
+- distributed
+- hypothesis
+- graphviz
+- python-graphviz
+- codecov
+- cmake
+- ninja
+- boto3
+- jsonschema
+- numba
+- llvmlite
+- pip:
+  - shap
+  - awscli