Replaces build job with cross-compile (#384)

Publish builds binaries for all supported platforms with the
cross-compile job. Running the build job is redundant for this workflow
as the amd64 linux binary is overwritten by cross-compile anyway. Also
this can cause CI job to fail if build and cross-compile both persist
the same files to CI workspace. However, using cross-compile for publish
workflow and only build for regular PR workflow is a bit awkward and
adds unnecessary complexity to the CI workflow definition. It is far
simpler to just replace build with cross-compile. This means all PR
builds will attempt to build binaries for all supported platforms even
if we loadtest only linux amd64 right now. I think is a good outcome
anyway as PR CI jobs can now catch issues that prevent the collector
from building for any of the supported architectures. This also paves
the way to enable functional/integration/load testing for all platforms
and architectures.

.circleci/config.yml

@@ -103,12 +103,12 @@ workflows:
       - setup:
           requires:
             - checkout-commit
-      - build:
+      - cross-compile:
           requires:
             - setup
       - run-stability-tests:
           requires:
-            - build
+            - cross-compile 
       - publish-dev:
           requires:
             - run-stability-tests
@@ -126,12 +126,6 @@ workflows:
           filters:
             tags:
               only: /.*/
-      - build:
-          requires:
-            - setup
-          filters:
-            tags:
-              only: /.*/
       - build-examples:
           requires:
             - setup
@@ -146,7 +140,7 @@ workflows:
               only: /.*/
       - loadtest:
           requires:
-            - build
+            - cross-compile 
           filters:
             tags:
               only: /.*/
@@ -161,8 +155,7 @@ workflows:
             - lint
             - unit-tests
             - integration-tests
-            - build
-            - cross-compile
+            - cross-compile 
           filters:
             branches:
               ignore: /.*/
@@ -173,7 +166,7 @@ workflows:
             - lint
             - unit-tests
             - integration-tests
-            - build
+            - cross-compile 
           filters:
             branches:
               only: /master|release\/.+/
@@ -205,17 +198,6 @@ jobs:
           name: Checks
           command: make -j4 checklicense impi misspell
 
-  build:
-    executor: golang
-    steps:
-      - restore_workspace
-      - run:
-          name: Build collector for linux_amd64
-          command: make otelcontribcol
-      - persist_to_workspace:
-          root: ~/
-          paths: project/bin
-
   build-examples:
     docker:
       - image: cimg/go:1.14
@@ -234,6 +216,9 @@ jobs:
       - run:
           name: Build collector for all archs
           command: grep ^otelcontribcol-all-sys Makefile|fmt -w 1|tail -n +2|circleci tests split|xargs make
+      - persist_to_workspace:
+          root: ~/
+          paths: project/bin
 
   unit-tests:
     executor: golang