Do build and test in one step

Speed up build time by moving these two tasks to one step so that a new
container doesn't have to be spun up and the cached modules from the
build step are reused in the test step.

.drone.yml

@@ -3,14 +3,11 @@ kind: pipeline
 name: test
 
 steps:
-  - name: build
-    image: golang:1.12
-    commands:
-      - make build
 
   - name: test
     image: golang:1.12
     commands:
+      - make build
       - make test
 
   - name: check