Package configuration for libffi is not found in macOS while installing travis-cli

I am trying to install gem install travis to use travis-cli as per reference https://rubygems.org/gems/travis but getting below error.

Tried solution mentioned here https://github.com/ffi/ffi/issues/653 :

brew reinstall libffi
export LDFLAGS="-L/usr/local/opt/libffi/lib"
export PKG_CONFIG_PATH="/usr/local/opt/libffi/lib/pkgconfig"
gem install travis

package configuration for libffi is not found "xcrun clang -o conftest -I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0/universal-darwin16 -I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0/ruby/backward -I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0 -I…