Add libedit2 mixin for php dependency on bionic
Add libedit2 mixin for php dependency on bionic

* It is required by the readline module

[#174231368]

cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci