Find zenoh_cpp_vendor package from ROS 2 (#614)

Signed-off-by: Ian Chen <ichen@openrobotics.org>

Author: iche033

.github/ci/before_cmake.sh

@@ -0,0 +1,2 @@
+# Set ROS_DISTRO. This is needed for finding zenoh packages vendored by ROS 2
+export ROS_DISTRO="jazzy"

.github/ci/packages-noble.apt

@@ -1 +1,2 @@
 cppzmq-dev
+ros-jazzy-zenoh-cpp-vendor

CMakeLists.txt

@@ -108,12 +108,27 @@ gz_find_package(CPPZMQ REQUIRED PRIVATE
 
 ########################################
 # Find Zenoh
-find_package(zenohc)
-find_package(zenohcxx)
-if (NOT zenohcxx_DIR)
+
+find_package(zenohc QUIET)
+find_package(zenohcxx QUIET)
+
+# If both zenohc and zenohcpp packages are not found then
+# look for these pacakages installed by ROS 2 zenoh_cpp_vendor package
+if (NOT zenohc_FOUND AND NOT zenohcxx_FOUND)
+  # Set CMAKE_PREFIX_PATH in order to find ROS 2 packages from plain cmake
+  # package, see https://github.com/ament/ament_cmake/issues/304
+  set(ros2_zenoh_cmake_path "/opt/ros/$ENV{ROS_DISTRO}/opt/zenoh_cpp_vendor/lib/cmake")
+  if (EXISTS ${ros2_zenoh_cmake_path})
+    list(PREPEND CMAKE_PREFIX_PATH ${ros2_zenoh_cmake_path})
+    find_package(zenohc QUIET)
+    find_package(zenohcxx QUIET)
+  endif()
+endif ()
+
+if (NOT zenohcxx_FOUND)
   message (STATUS "Looking for zenohcxx - not found")
   set (HAVE_ZENOH OFF CACHE BOOL "HAVE ZENOH" FORCE)
-elseif (NOT zenohc_DIR)
+elseif (NOT zenohc_FOUND)
   message (STATUS "Looking for zenohc - not found")
   set (HAVE_ZENOH OFF CACHE BOOL "HAVE ZENOH" FORCE)
 else ()