Lldb fails to compile C dependency when debugging my app?

This may be more of an lldb question, but hopefully it's not too far off topic:

I've been developing a Swift Vapor app using Xcode that I intend to run on a Raspberry pi. Today I decided to see if that would work, and got everything set up and building, but when I run, it crashes unrwapping an optional. Figured I'd see if lldb could be helpful here, so I tried that, and after crashing, it tried to parse one of the C dependency's header, which it couldn't find:

$ lldb .build/aarch64-unknown-linux-gnu/debug/Run
(lldb) target create ".build/aarch64-unknown-linux-gnu/debug/Run"
Current executable set to '/home/pi/furnace-controller/.build/aarch64-unknown-linux-gnu/debug/Run' (aarch64).
(lldb) r
Process 17660 launched: '/home/pi/furnace-controller/.build/aarch64-unknown-linux-gnu/debug/Run' (aarch64)
[ INFO ] Running migration
[ INFO ] Running migration
[ INFO ] Attempting to connect to MODBUS
[ CRITICAL ] Unabled to connect to MODBUS, Unknown (2), trying again after delay…
[ NOTICE ] Server starting on
App/FurnaceManager.swift:98: Fatal error: Unexpectedly found nil while unwrapping an Optional value
Current stack trace:
0    libswiftCore.so                    0x0000007ff7dde998 swift_reportError + 64
1    libswiftCore.so                    0x0000007ff7e4f454 _swift_stdlib_reportFatalErrorInFile + 124
2    libswiftCore.so                    0x0000007ff7b8d4fc <unavailable> + 1475836
3    libswiftCore.so                    0x0000007ff7b8d29c <unavailable> + 1475228
4    libswiftCore.so                    0x0000007ff7b8cb44 _assertionFailure(_:_:file:line:flags:) + 232
5    Run                                0x00000055556ef8f8 <unavailable> + 1702136
6    libswift_Concurrency.so            0x0000007ff7f9556c <unavailable> + 255340
7    libswift_Concurrency.so            0x0000007ff7f95c4c swift_job_run + 92
8    libdispatch.so                     0x0000007ff7828f88 <unavailable> + 176008
9    libdispatch.so                     0x0000007ff7828d1c <unavailable> + 175388
10   libdispatch.so                     0x0000007ff78354ec <unavailable> + 226540
11   libpthread.so.0                    0x0000007ff78df628 <unavailable> + 34344
12   libc.so.6                          0x0000007ff6c3a01c <unavailable> + 876572
warning: (aarch64) /home/pi/furnace-controller/.build/aarch64-unknown-linux-gnu/debug/Run unable to load swift module "App" (failed to get module "App" from AST context:
<module-includes>:1:10: note: in file included from <module-includes>:1:
#include "libmodbus.h"
<many more related errors…>

Do I need to give lldb more information about where to find things? I would have hoped it could glean that from the built target app.