Add a test for custom targets

Author: tgross35

.github/workflows/main.yaml

@@ -195,6 +195,17 @@ jobs:
       run: ./ci/update-musl.sh
     - run: cargo clippy --workspace --all-targets
 
+  build-custom:
+    name: Custom target
+    runs-on: ubuntu-24.04
+    timeout-minutes: 10
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Rust
+      run: rustup update nightly --no-self-update && rustup default nightly
+    - uses: Swatinem/rust-cache@v2
+    - run: cargo build -p compiler_builtins -p libm --target etc/thumbv7em-none-eabi-custom.json
+
   benchmarks:
     name: Benchmarks
     timeout-minutes: 20
@@ -331,6 +342,7 @@ jobs:
   success:
     needs:
       - benchmarks
+      - build-custom
       - clippy
       - extensive
       - miri

etc/thumbv7em-none-eabi-custom.json

@@ -0,0 +1,23 @@
+{
+  "abi": "eabi",
+  "arch": "arm",
+  "c-enum-min-bits": 8,
+  "crt-objects-fallback": "false",
+  "data-layout": "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64",
+  "emit-debug-gdb-scripts": false,
+  "frame-pointer": "always",
+  "linker": "rust-lld",
+  "linker-flavor": "gnu-lld",
+  "llvm-floatabi": "soft",
+  "llvm-target": "thumbv7em-none-eabi",
+  "max-atomic-width": 32,
+  "metadata": {
+    "description": "Bare ARMv7E-M",
+    "host_tools": false,
+    "std": false,
+    "tier": 2
+  },
+  "panic-strategy": "abort",
+  "relocation-model": "static",
+  "target-pointer-width": "32"
+}