Older system/kernel compatibility

[Matthew-Whitlock]

Use sendfile instead of copy_file_range when compiling on systems with kernels too old to support copy_file_range and glibc too old to emulate it.

When using auto-install.py, enable passing cmake arguments to dependencies. Also only attempts to import some non-stock python libraries when necessary. (I must pass -DCMAKE_NO_SYSTEM_FROM_IMPORTED=ON for compiling w/ custom mpi installs on some systems)

[bnicolae]

On these older systems, is there a good justification to use sendfile vs. the read/write engine (i.e., by setting posix-io=rw)?

[bnicolae]

Given there read/write engine is a good alternative for older kernels + older glib that do not support the copy_file_range syscall or its emulation, this pull request will be closed