Turn TBB into publicly linked library

3rdparty/find_dependencies.cmake

@@ -1568,7 +1568,7 @@ if(OPEN3D_USE_ONEAPI_PACKAGES)
         PACKAGE TBB
         TARGETS TBB::tbb
     )
-    list(APPEND Open3D_3RDPARTY_PRIVATE_TARGETS_FROM_SYSTEM Open3D::3rdparty_tbb)
+    list(APPEND Open3D_3RDPARTY_PUBLIC_TARGETS_FROM_SYSTEM Open3D::3rdparty_tbb)
 
 else(OPEN3D_USE_ONEAPI_PACKAGES)
     # MKL/BLAS
@@ -1687,7 +1687,7 @@ else(OPEN3D_USE_ONEAPI_PACKAGES)
             INCLUDE_DIRS ${STATIC_MKL_INCLUDE_DIR}
             LIB_DIR      ${STATIC_MKL_LIB_DIR}
             LIBRARIES    ${STATIC_MKL_LIBRARIES}
-            DEPENDS      ext_tbb ext_mkl_include ext_mkl
+            DEPENDS      Open3D::3rdparty_tbb ext_mkl_include ext_mkl
         )
         if(UNIX)
             target_compile_options(3rdparty_blas INTERFACE "$<$<COMPILE_LANGUAGE:CXX>:-m64>")
@@ -1709,9 +1709,13 @@ else(OPEN3D_USE_ONEAPI_PACKAGES)
     endif()
     if(NOT USE_SYSTEM_TBB)
         include(${Open3D_3RDPARTY_DIR}/mkl/tbb.cmake)
-        list(APPEND Open3D_3RDPARTY_PRIVATE_TARGETS_FROM_CUSTOM TBB::tbb)
+        add_library(3rdparty_tbb INTERFACE)
+        add_library(Open3D::3rdparty_tbb ALIAS 3rdparty_tbb)
+        target_link_libraries(3rdparty_tbb INTERFACE TBB::tbb)
+        install(TARGETS 3rdparty_tbb EXPORT ${PROJECT_NAME}Targets)
+        list(APPEND Open3D_3RDPARTY_PUBLIC_TARGETS_FROM_CUSTOM Open3D::3rdparty_tbb)
     else()
-        list(APPEND Open3D_3RDPARTY_PRIVATE_TARGETS_FROM_SYSTEM Open3D::3rdparty_tbb)
+        list(APPEND Open3D_3RDPARTY_PUBLIC_TARGETS_FROM_SYSTEM Open3D::3rdparty_tbb)
     endif()
 
 endif(OPEN3D_USE_ONEAPI_PACKAGES)