GitHub: separate build caches

To avoid build caches getting larger and larger, causing our builds to
fail, we separate the caches of the different job types.
If we don't separate them, then the caches can end up being a
combination of the different jobs, which isn't useful (for example the
build cache of the cross compilation build isn't useful in an
integration test and vice versa).

.github/workflows/main.yml

@@ -154,6 +154,7 @@ jobs:
         uses: ./.github/actions/setup-go
         with:
           go-version: '${{ env.GO_VERSION }}'
+          key-prefix: cross-compile
 
       - name: build release for all architectures
         run: make release
@@ -211,6 +212,7 @@ jobs:
         uses: ./.github/actions/setup-go
         with:
           go-version: '${{ env.GO_VERSION }}'
+          key-prefix: unit-test
 
       - name: install bitcoind
         run: ./scripts/install_bitcoind.sh
@@ -266,6 +268,7 @@ jobs:
         uses: ./.github/actions/setup-go
         with:
           go-version: '${{ env.GO_VERSION }}'
+          key-prefix: integration-test
 
       - name: install bitcoind
         run: ./scripts/install_bitcoind.sh
@@ -302,6 +305,7 @@ jobs:
         uses: ./.github/actions/setup-go
         with:
           go-version: '${{ env.GO_VERSION }}'
+          key-prefix: integration-test
 
       - name: run itest
         run: make itest-parallel windows=1