CMake macro to find the assimp library (#278)

Signed-off-by: Luca Della Vedova <[email protected]>

cmake/FindGzAssimp.cmake

@@ -0,0 +1,36 @@
+#===============================================================================
+# Copyright (C) 2022 Open Source Robotics Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+########################################
+# Find Assimp
+
+include(GzPkgConfig)
+
+if(ASSIMP_FIND_VERSION)
+  gz_pkg_check_modules_quiet(GzAssimp "assimp >= ${ASSIMP_FIND_VERSION}")
+else()
+  gz_pkg_check_modules_quiet(GzAssimp "assimp")
+endif()
+
+if(NOT ASSIMP_FOUND)
+  include(GzManualSearch)
+  gz_manual_search(ASSIMP
+                   HEADER_NAMES "assimp/scene.h"
+                   LIBRARY_NAMES "assimp")
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(
+    GzAssimp
+    REQUIRED_VARS GzAssimp_FOUND)
+endif()