double square brackets for if are not working in travis

Author: albestro

.travis.yml

@@ -108,9 +108,9 @@ matrix:
 
 before_script:
   - mkdir -p /tmp/cmake.root
-  - [[ $TRAVIS_OS_SUFFIX = 'linux' ]]; then CMAKE_PKG_SUFFIX="linux-x86_64"; else CMAKE_PKG_SUFFIX="macos10.10-universal"; fi
+  - if [ $TRAVIS_OS_SUFFIX = 'linux' ]; then CMAKE_PKG_SUFFIX="linux-x86_64"; else CMAKE_PKG_SUFFIX="macos10.10-universal"; fi
   - wget -qO- "https://cmake.org/files/v3.20/cmake-3.20.5-$CMAKE_PKG_SUFFIX.tar.gz" | tar --strip-components=1 -xz -C /tmp/cmake.root
-  - [[ $TRAVIS_OS_SUFFIX = 'linux' ]]; then CMAKE_BIN_DIR="CMake.app/Contents/bin"; else CMAKE_BIN_DIR="bin"; fi
+  - if [ $TRAVIS_OS_SUFFIX = 'linux' ]; then CMAKE_BIN_DIR="CMake.app/Contents/bin"; else CMAKE_BIN_DIR="bin"; fi
   - export PATH=/tmp/cmake.root/$CMAKE_BIN_DIR:$PATH
 
 # Build and check this project