Disallow skipping tx-sync tests in CI

Previously, we'd always skip tx-sync tests if the
`BITCOIND_EXE`/`ELECTRS_EXE` environment variables would be unset. While
this is especially fine for local testing, we still want to enforce
tests failing if somehow the `bitcoind`/`electrs` downloading or caching
in CI stops working. Here, we therefore add a `CI_ENV` variable that
indicates we're indeed running in CI, and only skip if it's unset.

Author: tnull

.github/workflows/build.yml

@@ -66,7 +66,7 @@ jobs:
             echo "ELECTRS_EXE=$( pwd )/bin/electrs-${{ runner.os }}-${{ runner.arch }}" >> "$GITHUB_ENV"
       - name: Run CI script
         shell: bash # Default on Winblows is powershell
-        run: CI_MINIMIZE_DISK_USAGE=1 ./ci/ci-tests.sh
+        run: CI_ENV=1 CI_MINIMIZE_DISK_USAGE=1 ./ci/ci-tests.sh
 
   coverage:
     strategy:

ci/ci-tests.sh

@@ -44,7 +44,7 @@ cargo check --verbose --color always --features rpc-client,rest-client,tokio
 popd
 
 if [[ "$HOST_PLATFORM" != *windows* ]]; then
-	if [ -z "$BITCOIND_EXE" ] || [ -z "$ELECTRS_EXE" ]; then
+	if [ -z "$CI_ENV" ] && [[ -z "$BITCOIND_EXE" || -z "$ELECTRS_EXE" ]]; then
 		echo -e "\n\nSkipping testing Transaction Sync Clients due to BITCOIND_EXE or ELECTRS_EXE being unset."
 	else
 		echo -e "\n\nBuilding and testing Transaction Sync Clients with features"