Use prebuilt gnullvm target

Author: mati865

.github/workflows/cross.yml

@@ -38,7 +38,7 @@ jobs:
 
       - name: Add toolchain target
         run: rustup target add ${{ matrix.target }}
-        if: contains(matrix.target, 'gnullvm') == false
+        if: contains(matrix.target, 'gnullvm') == false || startsWith(matrix.image, 'ubuntu-') && contains(matrix.target, 'gnullvm') && matrix.version == 'nightly'
 
       - name: Add nightly toolchain with rust-src
         run: |
@@ -83,10 +83,10 @@ jobs:
           }
         if: contains(matrix.target, 'gnullvm') == false
 
-      - name: Test with build-std
+      - name: Test gnullvm
         shell: pwsh
         run: |
-          cargo test --no-run --target ${{ matrix.target }} -Z build-std -p test_win32
+          cargo test --no-run --target ${{ matrix.target }} -p test_win32
           if (-Not (Resolve-Path "target/*/debug/deps/test_win32-*.exe" | Test-Path)) {
             throw "Failed to find test_win32 executable."
           }