Add support to release Linux aarch64 wheels

Problem
---------
On aarch64, ‘pip install dyNET’ builds the wheels from source code and is giving below error:
```
[ 71%] Building CXX object dynet/CMakeFiles/dynet.dir/nodes-random.cc.o
/tmp/pip-install-u5zcjrap/dyNET/dynet/mem.cc:13:10: fatal error: mm_malloc.h: No such file or directory
13 | #include
| ^~~~~~~~~~~~~
compilation terminated.
make[2]: *** [dynet/CMakeFiles/dynet.dir/build.make:297: dynet/CMakeFiles/dynet.dir/mem.cc.o] Error 1
make[2]: *** Waiting for unfinished jobs....
/tmp/pip-install-u5zcjrap/dyNET/dynet/lstm.cc: In member function ‘void dynet::SparseLSTMBuilder::set_sparsity(float)’:
/tmp/pip-install-u5zcjrap/dyNET/dynet/lstm.cc:686:19: warning: comparison of integer expressions of different signedness: ‘int’ and ‘unsigned int’ [-Wsign-compare]
686 | for (int i=0;i&, const std::vector&, const std::vector&)’:
/tmp/pip-install-u5zcjrap/dyNET/dynet/expr.cc:201:74: warning: comparison of integer expressions of different signedness: ‘const value_type’ {aka ‘const int’} and ‘unsigned int’ [-Wsign-compare]
201 | for(unsigned d=0;d

Start with the linked commit and Travis build, then reproduce the aarch64 installation and run test.py. Investigate where the test run stalls after the reported output. Done means Linux aarch64 wheels are published so pip install dyNET downloads them and the test suite completes successfully.

Written by the indexing model from the issue text.