ci(musl): move -crt-static to .cargo/config.toml

Add -C target-feature=-crt-static to the musl target rustflags in
.cargo/config.toml so it applies for all musl builds (local and cross).
Keep it in the CI RUSTFLAGS override as well since the env var overrides
both [build] and [target] level config.

https://claude.ai/code/session_01R3RoGqPDBRtNa2NRg3SeBM

Author: claude

.cargo/config.toml

@@ -6,8 +6,10 @@ bindeps = true
 
 # Linker wrappers for musl targets. On Linux hosts these use the system cc directly;
 # on non-Linux hosts (macOS, Windows) they cross-compile via cargo-zigbuild.
+# -crt-static: link musl dynamically so fspy preload .so can be injected into
+# host processes that are themselves dynamically linked (e.g. node on Alpine).
 [target.x86_64-unknown-linux-musl]
-rustflags = ["-C", "linker=.cargo/zigcc-x86_64-unknown-linux-musl"]
+rustflags = ["-C", "target-feature=-crt-static", "-C", "linker=.cargo/zigcc-x86_64-unknown-linux-musl"]
 
 [target.aarch64-unknown-linux-musl]
-rustflags = ["-C", "linker=.cargo/zigcc-aarch64-unknown-linux-musl"]
+rustflags = ["-C", "target-feature=-crt-static", "-C", "linker=.cargo/zigcc-aarch64-unknown-linux-musl"]

.github/workflows/ci.yml

@@ -144,9 +144,8 @@ jobs:
     env:
       # Override all rustflags to skip the zig cross-linker from .cargo/config.toml.
       # Alpine's cc is already musl-native, so no custom linker is needed.
-      # Must mirror [build].rustflags from .cargo/config.toml.
-      # -crt-static: link musl dynamically so fspy preload .so can be injected into
-      # host processes that are themselves dynamically linked (e.g. node on Alpine).
+      # Must mirror [build].rustflags and target rustflags from .cargo/config.toml
+      # (RUSTFLAGS env var overrides both levels).
       RUSTFLAGS: --cfg tokio_unstable -D warnings -C target-feature=-crt-static
     steps:
       - name: Install Alpine dependencies