fix CI

From previous experiment, ncurses is available in the CI environment so it's not
the problem. After some researching, I think it's the version of glibc being too
old (2.24 but purescript installer needs 2.27).

I see people upgrade glibc directly in Dockerfile like

ENV GLIBC_VERSION 2.25-r0

but we are using a docker image from CircleCI.

Let me try overwriting it by adding to `environment` variables.

Author: boygao1992

.circleci/config.yml

@@ -5,6 +5,7 @@ defaults: &defaults
   docker:
     - image: circleci/node:10.15-browsers
   environment:
+    GLIBC_VERSION: 2.27-r0
     RTS_ARGS: +RTS -N2 -RTS
 
 jobs: