cmake: make glm an imported target

cmake/modules/FindGLM.cmake

@@ -63,3 +63,10 @@ IF(GLM_FOUND)
         MESSAGE(STATUS "GLM_INCLUDE_DIR = ${GLM_INCLUDE_DIR}")
     ENDIF(NOT GLM_FIND_QUIETLY)
 ENDIF(GLM_FOUND)
+
+if(GLM_FOUND)
+  add_library(glm::glm INTERFACE IMPORTED)
+  set_target_properties(glm::glm PROPERTIES
+    INTERFACE_INCLUDE_DIRECTORIES "${GLM_INCLUDE_DIR}"
+    )
+endif()

rwengine/CMakeLists.txt

@@ -148,6 +148,7 @@ add_library(rwengine
 target_link_libraries(rwengine
     PUBLIC
         rwlib
+        glm::glm
     PRIVATE
         ${FFMPEG_LIBRARIES}
         ${OPENAL_LIBRARY}