GitHub: run cross compilation for all architectures

Because we now have conditionally compiled code that depends on the
architecture it is built for, we want to make sure we can build all
architectures that we also release. Since GitHub builds are very fast,
we can easily do this instead of only compiling for certain select
architectures.

.github/workflows/main.yml

@@ -129,12 +129,6 @@ jobs:
   cross-compile:
     name: cross compilation
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        build_sys:
-          - windows-amd64
-          - freebsd-amd64
-          - solaris-amd64
     steps:
       - name: git checkout
         uses: actions/checkout@v2
@@ -155,8 +149,8 @@ jobs:
         with:
           go-version: '~${{ env.GO_VERSION }}'
 
-      - name: build release for architecture
-        run: make release sys=${{ matrix.build_sys }}
+      - name: build release for all architectures
+        run: make release
 
   ########################
   # mobile compilation