build: Unaligned libsecp256k1 flags in debug builds

[hebasto]

When configured with --enable-debug, C++ code compiles with -O0 -g3.

However, libsecp256k1 code compiles with -g -O2.

[theuni]

I'm not sure this is a problem? It's hard to imagine a use-case where we'd want to be debugging Core with an un-optimized secp.

[fanquake]

What's the status of this? Can you explain the use-case where this is an issue for you, or the other motivation?