Build tarpaulin from scratch for now

.travis.yml

@@ -23,8 +23,9 @@ rust:
 before_script:
   - |
     if [[ "$TRAVIS_RUST_VERSION" == "nightly"* ]]; then rustup component add rustfmt-preview; fi
+before_cache:
   - |
-    if [[ "$TRAVIS_RUST_VERSION" == stable ]] 2> /dev/null && [ -z "$ELEFREN_FEATURES" ] 2>/dev/null && [[ "$TRAVIS_OS_NAME" == "linux" ]] 2>/dev/null && [[ -z "$(which cargo-tarpaulin)" ]]; then
+    if [[ "$TRAVIS_RUST_VERSION" == "nightly"* ]] 2> /dev/null && [ -z "$ELEFREN_FEATURES" ] 2>/dev/null && [[ "$TRAVIS_OS_NAME" == "linux" ]] 2>/dev/null; then
       RUSTFLAGS="--cfg procmacro2_semver_exempt" cargo install cargo-tarpaulin
     fi
 script: