ci: add beta workaround due to rust-lang/rust#60846

Author: ipetkov

.travis.yml

@@ -16,7 +16,8 @@ matrix:
   include:
     - rust: nightly
       cache: false
-      sudo: required # Work around for travis-ci/travis-ci#9061
+      # FIXME: turn this back on when code coverage is enabled
+      #sudo: required # Work around for travis-ci/travis-ci#9061
       env:
         - RUSTFLAGS="-C link-dead-code" # Enable better code coverage at the cost of binary size
       script:
@@ -35,6 +36,20 @@ matrix:
       #  - ./ci/install-kcov.sh && ./ci/coverage.sh
 
     - rust: beta
+      # FIXME: temporarily building without default features on beta as well due to rust-lang/rust#60846
+      script:
+        - cargo check --no-default-features
+          # NB: don't run with the top-level feature enabled see rust-lang/rust#60444
+        - cargo check --no-default-features --features 'conch-parser'
+          # Retry with fewer cores if the initial `cargo test` fails to work around possible OOM errors
+          # for more details see https://github.com/rust-lang/cargo/issues/4415
+        - cargo test --no-fail-fast --no-default-features --features 'conch-parser' ||
+          (
+            echo 'initial `cargo test` failed, retrying with fewer cores to work around OOM issues' &&
+            cargo test --no-fail-fast --verbose -j 1
+            cargo test --no-fail-fast --no-default-features --features 'conch-parser'
+          )
+
     - rust: stable
     - rust: 1.26.0
     - os: osx