fix setting CARGO_BUILD_TARGET

Author: davidhewitt

.github/workflows/build.yml

@@ -25,6 +25,11 @@ jobs:
     continue-on-error: ${{ endsWith(inputs.python-version, '-dev') || contains(fromJSON('["3.7", "3.8"]'), inputs.python-version) || contains(fromJSON('["beta", "nightly"]'), inputs.rust) }}
     runs-on: ${{ inputs.os }}
     if: ${{ !(startsWith(inputs.python-version, 'graalpy') && startsWith(inputs.os, 'windows')) }}
+    env:
+      # On windows 32 bit, we are running on an x64 host, so we need to specifically set the target
+      # NB we don't do this for *all* jobs because it breaks coverage of proc macros to have an
+      # explicit target set.
+      CARGO_BUILD_TARGET: ${{ (inputs.os == 'windows-latest' && inputs.python-architecture == 'x86' && inputs.rust-target) || '' }}
     steps:
       - uses: actions/checkout@v4
         with:
@@ -59,13 +64,6 @@ jobs:
           # rust-src needed to correctly format errors, see #1865
           components: rust-src,llvm-tools-preview
 
-      # On windows 32 bit, we are running on an x64 host, so we need to specifically set the target
-      # NB we don't do this for *all* jobs because it breaks coverage of proc macros to have an
-      # explicit target set.
-      - if: ${{ inputs.os == 'windows-latest' && inputs.python-architecture == 'x86' }}
-        name: Set cargo target
-        run: echo "CARGO_BUILD_TARGET=${{ inputs.rust-target }}" >> $GITHUB_ENV
-
       - uses: Swatinem/rust-cache@v2
         with:
           save-if: ${{ github.ref == 'refs/heads/main' || contains(github.event.pull_request.labels.*.name, 'CI-save-pr-cache') }}