gha/rpk-build: test linux and darwin, exclude from compile

(cherry picked from commit c721fb2)

Author: andrewhsu

.github/workflows/rpk-build.yml

@@ -24,6 +24,11 @@ jobs:
       matrix:
         goos: [linux, darwin, windows]
         goarch: [amd64, arm64]
+        exclude:
+          - goos: linux
+            goarch: amd64
+          - goos: darwin
+            goarch: arm64
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
@@ -34,7 +39,10 @@ jobs:
       - run: GOOS=${{ matrix.goos }} GOARCH=${{ matrix.goarch }} go build -o rpk cmd/rpk/main.go
         working-directory: src/go/rpk/
   test:
-    runs-on: ubuntu-24.04
+    strategy:
+      matrix:
+        runner: [ubuntu-24.04, macos-15]
+    runs-on: ${{ matrix.runner }}
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-go@v5