Add custom build step for libsecp256k1

.circleci/config.yml

@@ -14,6 +14,8 @@ jobs:
     working_directory: ~/app
 
     steps:
+      - run: apt-get update; apt-get -y install autoconf build-essential libgmp3-dev libtool
+
       - checkout
 
       - run: mix local.hex --force
@@ -70,6 +72,11 @@ jobs:
 
       - run: mix compile
 
+      # Ensure NIF is compiled for libsecp256k1
+      - run:
+          command: make
+          working_directory: "deps/libsecp256k1"
+
       # `deps` needs to be cached with `_build` because `_build` will symlink into `deps`
 
       - save_cache: