feat: make CMD subprocesses match build_platform architecture when running emulated

.github/workflows/rust.yml

@@ -110,10 +110,56 @@ jobs:
           PREFIX_DEV_READ_ONLY_TOKEN: ${{ secrets.PREFIX_DEV_READ_ONLY_TOKEN }}
           S3_ACCESS_KEY_ID: ${{ secrets.S3_UPLOAD_ACCESS_KEY_ID }}
           S3_SECRET_ACCESS_KEY: ${{ secrets.S3_UPLOAD_ACCESS_KEY_SECRET }}
+      - name: Stage x64 release binary
+        if: matrix.os == 'windows-latest'
+        shell: pwsh
+        run: |
+          $binary = Get-ChildItem target-pixi -Recurse -Filter rattler-build.exe |
+            Where-Object { $_.DirectoryName -match "\\release$" } |
+            Select-Object -First 1
+          if ($null -eq $binary) {
+            throw "Could not find the x64 release binary."
+          }
+          New-Item -ItemType Directory -Path staging | Out-Null
+          Copy-Item $binary.FullName staging/rattler-build.exe
+      - name: Upload x64 release binary
+        if: matrix.os == 'windows-latest'
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v4.4.0
+        with:
+          name: rattler-build-windows-x64-e2e
+          path: staging/rattler-build.exe
+          if-no-files-found: error
       - name: Show sccache stats
         if: always()
         run: pixi run sccache --show-stats
 
+  windows-arm-e2e-test:
+    name: End-to-end (windows-11-arm)
+    needs: e2e-test
+    # e2e-test is a matrix job. Run this when another platform fails, provided
+    # the workflow itself was not cancelled, so an unrelated failure does not
+    # skip validation of the successfully uploaded Windows x64 binary.
+    if: ${{ always() && !cancelled() }}
+    runs-on: windows-11-arm
+    steps:
+      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          submodules: recursive
+          persist-credentials: false
+      - uses: prefix-dev/setup-pixi@a09b6247153796b190642a2b53fac4241043cf6f # v0.10.0
+        with:
+          cache: true
+          cache-write: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
+      - name: Download x64 release binary
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: rattler-build-windows-x64-e2e
+          path: bin
+      - name: Run Windows architecture E2E test
+        run: pixi run --platform win-64 --frozen pytest test/end-to-end/test_windows_architecture_execution.py -v
+        env:
+          RATTLER_BUILD_PATH: ${{ github.workspace }}\bin\rattler-build.exe
+
   rebuild-test:
     name: Rebuild Test
     if: contains(github.event.pull_request.labels.*.name, 'needs-rebuild-tests')

crates/rattler_build_core/src/env_vars.rs

@@ -203,6 +203,7 @@ pub fn os_vars(
     prefix: &Path,
     target_platform: &Platform,
     host_platform: &Platform,
+    build_platform: &Platform,
     env_isolation: EnvironmentIsolation,
     work_dir: &Path,
 ) -> HashMap<String, Option<String>> {
@@ -260,13 +261,12 @@ pub fn os_vars(
             env_isolation,
         ));
     }
-    let build_platform = Platform::current();
     if build_platform.is_windows() {
-        vars.extend(windows::env::default_env_vars_build(&build_platform));
+        vars.extend(windows::env::default_env_vars_build(build_platform));
     } else if build_platform.is_osx() {
-        vars.extend(macos::env::default_env_vars_build(&build_platform));
+        vars.extend(macos::env::default_env_vars_build(build_platform));
     } else if build_platform.is_linux() {
-        vars.extend(linux::env::default_env_vars_build(&build_platform));
+        vars.extend(linux::env::default_env_vars_build(build_platform));
     }
 
     if build_platform.is_windows() {
@@ -502,6 +502,7 @@ mod test {
             prefix,
             &Platform::NoArch,
             &Platform::Win64,
+            &Platform::Win64,
             EnvironmentIsolation::Strict,
             work_dir,
         );
@@ -516,6 +517,25 @@ mod test {
         );
     }
 
+    #[test]
+    fn build_vars_follow_configured_build_platform() {
+        let vars = os_vars(
+            Path::new("/some/prefix"),
+            &Platform::WinArm64,
+            &Platform::WinArm64,
+            &Platform::WinArm64,
+            EnvironmentIsolation::Strict,
+            Path::new("/some/work"),
+        );
+
+        let expected =
+            std::env::var("BUILD").unwrap_or_else(|_| "arm64-pc-windows-19.0.0".to_string());
+        assert_eq!(
+            vars.get("BUILD").and_then(|value| value.as_deref()),
+            Some(expected.as_str())
+        );
+    }
+
     /// noarch on a non-Windows host does not emit Windows target vars.
     #[test]
     fn test_noarch_non_windows_host_has_no_windows_vars() {
@@ -526,6 +546,7 @@ mod test {
             prefix,
             &Platform::NoArch,
             &Platform::Linux64,
+            &Platform::Linux64,
             EnvironmentIsolation::Strict,
             work_dir,
         );