[#3] Control Cirrus CI via global variable

.cirrus.yml

@@ -12,6 +12,20 @@
 
 ---
 
+#
+# Global environment variables
+#
+
+env:
+  CI_ENABLED: true
+  # RUSTFLAGS: "-C debug-assertions"
+
+#
+# Filter to run the CI only on the main branch or for pull request to the main branch
+#
+
+only_if: $CI_ENABLED && ( $CIRRUS_BRANCH == 'main' || ($CIRRUS_PR != '' && $CIRRUS_BASE_BRANCH == 'main'))
+
 #
 # Templates
 #
@@ -130,19 +144,6 @@ iox2_freebsd_setup_template: &IOX2_FREEBSD_SETUP
     - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal --no-modify-path
     - rustup component add clippy rustfmt
 
-#
-# Filter to run the CI only on the main branch or for pull request to the main branch
-#
-
-only_if: false && ( $CIRRUS_BRANCH == 'main' || ($CIRRUS_PR != '' && $CIRRUS_BASE_BRANCH == 'main'))
-
-#
-# Global environment variables
-#
-
-# env:
-  # RUSTFLAGS: "-C debug-assertions"
-
 #
 # Preflight-Check with Ubuntu x86 stable debug
 #