Move OBJ handling to a mjpDecoder.

PiperOrigin-RevId: 875194599
Change-Id: I2cccc683d69a217f1817e70d16bc1815e366d00c

test/user/CMakeLists.txt

@@ -12,7 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-mujoco_test(user_model_test ADDITIONAL_LINK_LIBRARIES absl::str_format)
+mujoco_test(
+  user_model_test
+  PROPERTIES
+  ENVIRONMENT
+  "MUJOCO_PLUGIN_DIR=$<TARGET_FILE_DIR:obj_decoder>"
+  ADDITIONAL_LINK_LIBRARIES absl::str_format
+)
 
 mujoco_test(user_objects_test)
 
@@ -23,9 +29,20 @@ mujoco_test(
   "MUJOCO_PLUGIN_DIR=$<TARGET_FILE_DIR:elasticity>"
 )
 
-mujoco_test(user_flex_test)
+mujoco_test(
+  user_flex_test
+  PROPERTIES
+  ENVIRONMENT
+  "MUJOCO_PLUGIN_DIR=$<TARGET_FILE_DIR:obj_decoder>"
+)
 
-mujoco_test(user_mesh_test ADDITIONAL_LINK_LIBRARIES absl::str_format)
+mujoco_test(
+  user_mesh_test
+  PROPERTIES
+  ENVIRONMENT
+  "MUJOCO_PLUGIN_DIR=$<TARGET_FILE_DIR:obj_decoder>"
+  ADDITIONAL_LINK_LIBRARIES absl::str_format
+)
 
 mujoco_test(user_composite_test)