build: Make backtraces useable in release builds

Having `strip = "symbols"` and omitting `-C force-unwind-tables` makes backtraces generated with `RUST_BACKTRACE=1` completely useless in release builds.

By adding the `-C force-unwind-tables` flag and setting `strip = "debuginfo"`, we make backtraces usable in release builds. This will help us debug issues we are unable to reproduce, since we can ask users to set `RUST_BACKTRACE=1` and provide the logs with this option.

.cargo/config.toml

@@ -1,2 +1,5 @@
+[build]
+rustflags = ["-C", "force-unwind-tables"] # Make backtraces work.
+
 [target.'cfg(all(windows, target_env = "msvc"))']
 rustflags = ["-C", "target-feature=+crt-static"]

Cargo.toml

@@ -113,7 +113,7 @@ winapi = "0.3.9"
 [profile.release]
 opt-level = "z"
 panic = "abort"
-strip = true      # Strip symbols from the binary.
-codegen-units = 1 # Parallel compilation prevents some optimizations.
+strip = "debuginfo" # Only strip debuginfo (not symbols) to keep backtraces useful.
+codegen-units = 1   # Parallel compilation prevents some optimizations.
 # We do not enable link-time optimizations (lto) because they cause the
 # CLI to timeout when run in Xcode Cloud.