message: ci: tweak minimum supported Rust handling
  lazy_static 1.2 bumped its MSRV to Rust 1.24.1, so we rollback to using
  lazy_static 1.1 when testing on Rust versions older than 1.24.1.
diff: # This is the main CI script for testing the regex crate and its sub-crates.
  set -ex
  +MSRV="1.20.0"
  +
  +# If we're building on 1.20, then lazy_static 1.2 will fail to build since it
  +# updated its MSRV to 1.24.1. In this case, we force the use of lazy_static 1.1
  +# to build on Rust 1.20.0.
  +if [ "$TRAVIS_RUST_VERSION" = "$MSRV" ]; then
  + cargo update -p lazy_static --precise 1.1.0
  +fi
  # Builds the regex crate and runs tests.
  cargo build --verbose
  @@ -13,7 +21,7 @@ cargo doc --verbose
  # more frequently, and therefore might require a newer version of Rust.
  #
  # This isn't ideal. It's a compromise.
  -if [ "$TRAVIS_RUST_VERSION" = "1.20.0" ]; then
  +if [ "$TRAVIS_RUST_VERSION" = "$MSRV" ]; then
  exit
  fi
  