ci: avoid duplicate builds for two CI builds

.github/workflows/ci-build.yml

@@ -44,6 +44,8 @@ jobs:
     # Enable sccache via environment variable
     # env:
       # RUSTC_WRAPPER: /home/ubuntu/.cargo/bin/sccache
+    # a push event from the origin repo, or a PR from external repo
+    if: ${{ github.event_name == 'push' || github.event.pull_request.head.repo.full_name != 'nymtech/nym' }}
     steps:
       - name: Install Dependencies (Linux)
         run: sudo apt-get update && sudo apt-get -y install libwebkit2gtk-4.0-dev build-essential curl wget libssl-dev libgtk-3-dev libudev-dev squashfs-tools protobuf-compiler

.github/workflows/ci-nym-connect-desktop-rust.yml

@@ -27,6 +27,8 @@ jobs:
     runs-on: [self-hosted, custom-linux]
     # env:
     #   RUSTC_WRAPPER: /home/ubuntu/.cargo/bin/sccache
+    # a push event from the origin repo, or a PR from external repo
+    if: ${{ github.event_name == 'push' || github.event.pull_request.head.repo.full_name != 'nymtech/nym' }}
     steps:
       - name: Install Dependencies (Linux)
         run: sudo apt-get update && sudo apt-get -y install libwebkit2gtk-4.0-dev build-essential curl wget libssl-dev libgtk-3-dev squashfs-tools libayatana-appindicator3-dev