refactor(.github/workflows): macos, windows: use ./make, run less frequently (#333)

Like in the previous PR, here we make macos and windows builds only run when we're preparing a release. While there, migrate the code to use the `./make` script. Tested in https://github.com/ooni/probe-cli/pull/331.

Reference issue is https://github.com/ooni/probe/issues/1466

.github/workflows/macos.yml

@@ -1,20 +1,13 @@
-# Build and test macOS binary
+# macos builds ooniprobe for macos
 name: macos
 on:
   push:
-  schedule:
-    - cron: "14 17 * * 3"
+    branches:
+      - "release/**"
 jobs:
   build:
-    runs-on: "macos-latest"
+    runs-on: "macos-10.15"
     steps:
-      - uses: actions/setup-go@v1
-        with:
-          go-version: "1.16"
       - uses: actions/checkout@v2
-      - run: ./build.sh darwin
+      - run: ./make --disable-embedding-psiphon-config -t ./CLI/darwin/amd64/ooniprobe
       - run: ./smoketest.sh ./CLI/darwin/amd64/ooniprobe
-      - uses: actions/upload-artifact@v1
-        with:
-          name: ooniprobe-darwin-amd64
-          path: ./CLI/darwin/amd64/ooniprobe