make sure we use software float when building arm binary

our switches don't have a hardware floating point unit which is set by default when building arm v7 or v6. It seems that setting arm to v5 would also work 
golang/go#61588

.github/workflows/main.yml

@@ -24,7 +24,6 @@ jobs:
         # build and publish in parallel: linux/amd64, linux/arm64, linux/arm
         goos: ["linux"]
         goarch: ["amd64", "arm", "arm64"]
-        goarm: "7"
     steps:
       - name: Check out the tag reference into the Go module directory
         uses: actions/checkout@v3
@@ -39,7 +38,7 @@ jobs:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           goos: ${{ matrix.goos }}
           goarch: ${{ matrix.goarch }}
-          goarm: "7"
+          goarm: "7,softfloat"
           binary_name: "wireguard-go"
           release_name: "${{ env.GITHUB_REF_NAME }}"
           compress_assets: "OFF"