Fix disk usage of the coverage workflow

.github/workflows/coverage.yml

@@ -9,7 +9,9 @@ env:
   RUST_BACKTRACE: 1
   PRUSTI_ASSERT_TIMEOUT: 60000
   # Disable incremental builds to reduce disk usage
-  CARGO_INCREMENTAL: 1
+  CARGO_INCREMENTAL: 0  
+  # The /mnt disk has 66 GB of free space; more than the working directory
+  COVERAGE_PATH: /mnt/prusti-coverage
 
 jobs:
   test:
@@ -27,19 +29,11 @@ jobs:
       - name: Set up the environment
         run: python x.py setup
 
-      - name: Report disk usage
-        run: df -h
-
-      - name: Cache cargo
-        uses: Swatinem/rust-cache@v2
-        with:
-          shared-key: "shared"
-
       - name: Enable collection of source-based coverage
         run: |
           # The following are necessary for profiling (see https://github.com/mozilla/grcov)
           echo "RUSTFLAGS=-Cinstrument-coverage" >> $GITHUB_ENV
-          echo "LLVM_PROFILE_FILE=${GITHUB_WORKSPACE}/target/coverage/gcov-%p-%m.profraw" >> $GITHUB_ENV
+          echo "LLVM_PROFILE_FILE=${COVERAGE_PATH}/gcov-%p-%m.profraw" >> $GITHUB_ENV
 
       - name: Report disk usage
         run: df -h
@@ -50,9 +44,6 @@ jobs:
       - name: Report disk usage
         run: df -h
 
-      - name: Clear coverage generated by prusti-contracts-build
-        run: rm -rf target/coverage
-
       - name: Report disk usage
         run: df -h
 
@@ -89,7 +80,7 @@ jobs:
       - name: Collect coverage
         run: |
           curl -sL https://github.com/mozilla/grcov/releases/latest/download/grcov-x86_64-unknown-linux-gnu.tar.bz2 | tar jxf -
-          ./grcov . --llvm --binary-path ./target/debug/ -s . -t lcov --branch --ignore-not-existing --ignore "/*" -o lcov.info
+          ./grcov "$COVERAGE_PATH" --llvm --binary-path ./target/debug/ -s . -t lcov --branch --ignore-not-existing --ignore "/*" -o lcov.info
 
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@v1