dev-shell: Disable separateDebugInfo

[xokdvium]

Motivation

This breaks gdb pretty-printers inserted into .debug_gdb_scripts section, because it implies --compress-debug-sections=zlib, -Wa,--compress-debug-sections. This is very unfortunate, because then gdb can't use pretty printers for Boost.Unordered (which are very useful, since boost::unoredred_flat_map is impossible to debug). This seems perfectly fine to disable in the dev-shell for the time being.

See 1, 2, 3 for further references.

With this change I'm able to use boost's pretty-printers out-of-the box:

p *importResolutionCache
$2 = boost::concurrent_flat_map with 1 elements = {[{accessor = {p = std::shared_ptr<nix::SourceAccessor> (use count 5, weak count 1) = {
        get() = 0x555555d830a8}}, path = {static root = {static root = <same as static member of an already seen type>, path = "/"},
      path = "/derivation-internal.nix"}}] = {accessor = {p = std::shared_ptr<nix::SourceAccessor> (use count 5, weak count 1) = {
        get() = 0x555555d830a8}}, path = {static root = {static root = <same as static member of an already seen type>, path = "/"},
      path = "/derivation-internal.nix"}}}

When combined with a simple add-auto-load-safe-path ~/code in .gdbinit

Context

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[xokdvium]

cc @edolstra, @Ericson2314. Hope you appreciate the ability to once again debug unordered maps without jumping through hoops.

[cole-h]

I remember noticing this kind of error message last week when I was poking at the localhost bug, so nice to see it fixed so soon!