Make binary size check CI workflow platform independent.

- Use the platform-independent symlink to the build artefacts.
- Specify bash shell on steps that require it.

Author: detly

.github/actions/build-with-patched-std/action.yml

@@ -27,7 +27,10 @@ runs:
       id: measure
       env:
         RUSTC_FLAGS: -Copt-level=3 -Cstrip=symbols
-        RUSTC_BUILD_DIR: build/x86_64-unknown-linux-gnu
+        # This symlink is made by Build::new() in the bootstrap crate, using a
+        # symlink on Linux and a junction on Windows, so it will exist on both
+        # platforms.
+        RUSTC_BUILD_DIR: build/host
       working-directory: ${{ inputs.rustc-dir }}
       run: |
         rm -rf "$RUSTC_BUILD_DIR/stage0-std"

.github/workflows/check-binary-size.yml

@@ -31,6 +31,7 @@ jobs:
       binary-size-updated: ${{ steps.size-updated.outputs.test-binary-size }}
     steps:
       - name: Print info
+        shell: bash
         run: |
           echo "Current SHA: $HEAD_COMMIT"
           echo "Base SHA: $BASE_COMMIT"
@@ -47,6 +48,7 @@ jobs:
           repository: rust-lang/rust
           path: ${{ env.RUSTC_DIR }}
       - name: Set up std repository and backtrace submodule for size test
+        shell: bash
         working-directory: ${{ env.RUSTC_DIR }}
         run: |
           # Bootstrap config