1. only build py3.6 py3.9

2. remove --disable-shared to spit out libpython.so since pyinstaller need it (doesn't support static linked python)
3. update LD_LIBRARY_PATH to resolve problem brought in pypa#2 (to locate libpython.so when start python)
4. change default from py37 to py36 since py37 calls for libcrypt.so.2 which not available on all OS (at least rhel6/7)
5. add rust+pyinstaller installation to 2nd image