ci: fix env

Author: DaniPopes

.github/workflows/ci.yml

@@ -50,7 +50,9 @@ jobs:
         if: matrix.rust == 'nightly'
 
       - name: Enable target feature
-        run: echo RUSTFLAGS=${RUSTFLAGS}\ -Ctarget-feature=+${{ matrix.target.feature }} >> $GITHUB_ENV
+        run: |
+          echo RUSTFLAGS_BAK=$RUSTFLAGS >> $GITHUB_ENV
+          echo RUSTFLAGS=${RUSTFLAGS}\ -Ctarget-feature=+${{ matrix.target.feature }} >> $GITHUB_ENV
 
       - uses: Swatinem/rust-cache@v2
 
@@ -65,7 +67,7 @@ jobs:
         if: matrix.rust == 'nightly'
 
       - name: Disable target feature
-        run: echo RUSTFLAGS=${RUSTFLAGS}\ -Ctarget-feature=-${{ matrix.target.feature }} >> $GITHUB_ENV
+        run: echo RUSTFLAGS=${RUSTFLAGS_BAK}\ -Ctarget-feature=-${{ matrix.target.feature }} >> $GITHUB_ENV
 
       - run: cargo build
       - run: cargo build --no-default-features