Disable RTTI in C++ source

[pcapriotti]

This fixes a linker issue with libsnappy-1.1.9. Namely, RTTI has been disabled in 1.1.9 (see google/snappy@c98344f), but the haskell package is still compiling its C++ source file with RTTI enabled, which results in an unresolvable symbol (a typeinfo structure).

This PR migrates the cabal file to 2.2, and sets the cxx-sources and cxx-options field (just like #6) in order to disable RTTI.

More information

The libsnappy-1.1.9 shared object does not have any typeinfo symbols:

$ objdump -T /usr/lib/libsnappy.so | c++filt | grep typeinfo || echo "no matches"
no matches

Before this patch:

$ objdump -T dist-newstyle/build/x86_64-linux/ghc-8.10.4/snappy-0.2.0.2/build/libHSsnappy-0.2.0.2-inplace-ghc8.10.4.so | c++filt | grep typeinfo || echo "no matches"
0000000000000000      DO *UND*  0000000000000000              typeinfo for snappy::Source
0000000000008370  w   DO .rodata  000000000000000a  Base        typeinfo name for BSSource
0000000000009b90  w   DO .data.rel.ro 0000000000000018  Base        typeinfo for BSSource

After this patch:

$ objdump -T dist-newstyle/build/x86_64-linux/ghc-8.10.4/snappy-0.2.0.2/build/libHSsnappy-0.2.0.2-inplace-ghc8.10.4.so | c++filt | grep typeinfo || echo "no matches"
no matches