fix: scope rustflags to target triple to avoid SIGILL in build scripts (#91)

The previous fix (#90) switched from RUSTFLAGS to build.rustflags, but
build.rustflags still applies to build scripts. Use target-scoped
rustflags (target.'<triple>'.rustflags) so CPU flags only affect crate
compilation, leaving host build scripts unaffected.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ewels

.github/workflows/ci.yml

@@ -45,17 +45,21 @@ jobs:
 
       - uses: Swatinem/rust-cache@c19371144df3bb44fab255c43d04cbc2ab54d1c4 # ratchet:Swatinem/rust-cache@v2.9.1
 
+      - name: Detect host triple
+        if: matrix.target_cpu
+        run: echo "HOST_TRIPLE=$(rustc -vV | awk '/^host:/ {print $2}')" >> "$GITHUB_ENV"
+
       - name: Build
         run: >
           cargo build --release
-          ${TARGET_CPU:+--config "build.rustflags=['-C', 'target-cpu=$TARGET_CPU']"}
+          ${TARGET_CPU:+--config "target.'$HOST_TRIPLE'.rustflags=['-C', 'target-cpu=$TARGET_CPU']"}
         env:
           TARGET_CPU: ${{ matrix.target_cpu || '' }}
 
       - name: Test
         run: >
           cargo test --release
-          ${TARGET_CPU:+--config "build.rustflags=['-C', 'target-cpu=$TARGET_CPU']"}
+          ${TARGET_CPU:+--config "target.'$HOST_TRIPLE'.rustflags=['-C', 'target-cpu=$TARGET_CPU']"}
         env:
           TARGET_CPU: ${{ matrix.target_cpu || '' }}
 

.github/workflows/release.yml

@@ -124,7 +124,7 @@ jobs:
       - name: Build
         run: >
           cargo build --release --target ${{ matrix.target }}
-          ${TARGET_CPU:+--config "build.rustflags=['-C', 'target-cpu=$TARGET_CPU']"}
+          ${TARGET_CPU:+--config "target.'${{ matrix.target }}'.rustflags=['-C', 'target-cpu=$TARGET_CPU']"}
         env:
           TARGET_CPU: ${{ matrix.target_cpu || '' }}
 

Dockerfile

@@ -21,9 +21,10 @@ COPY Cargo.toml Cargo.lock build.rs ./
 COPY cpp/ cpp/
 COPY src/ src/
 
-RUN GIT_SHORT_HASH="${GIT_SHORT_HASH}" \
+RUN HOST_TRIPLE=$(rustc -vV | awk '/^host:/ {print $2}') && \
+    GIT_SHORT_HASH="${GIT_SHORT_HASH}" \
     cargo build --release \
-        ${CPU_TARGET:+--config "build.rustflags=['-C', 'target-cpu=$CPU_TARGET']"} \
+        ${CPU_TARGET:+--config "target.'$HOST_TRIPLE'.rustflags=['-C', 'target-cpu=$CPU_TARGET']"} \
     && strip target/release/rustqc
 
 # ---- Runtime stage ----