Make wasi-nn backends as separated shared libraries (#3509)

- All files under *core/iwasm/libraries/wasi-nn* are compiled as shared libraries
- *wasi-nn.c* is shared between backends
- Every backend has a separated shared library
- If wasi-nn feature is enabled, iwasm will depend on shared library libiwasm.so
  instead of linking static library libvmlib.a

core/iwasm/libraries/wasi-nn/cmake/wasi_nn.cmake

@@ -6,17 +6,51 @@ list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})
 # Find tensorflow-lite
 find_package(tensorflow_lite REQUIRED)
 
-set(WASI_NN_ROOT_DIR ${CMAKE_CURRENT_LIST_DIR}/..)
+set(WASI_NN_ROOT ${CMAKE_CURRENT_LIST_DIR}/..)
 
-include_directories (${WASI_NN_ROOT_DIR}/include)
-include_directories (${WASI_NN_ROOT_DIR}/src)
-include_directories (${WASI_NN_ROOT_DIR}/src/utils)
-
-set (
-  WASI_NN_SOURCES
-  ${WASI_NN_ROOT_DIR}/src/wasi_nn.c
-  ${WASI_NN_ROOT_DIR}/src/wasi_nn_tensorflowlite.cpp
-  ${WASI_NN_ROOT_DIR}/src/utils/wasi_nn_app_native.c
+#
+# wasi-nn general
+add_library(
+  wasi-nn-general
+  SHARED
+    ${WASI_NN_ROOT}/src/wasi_nn.c
+    ${WASI_NN_ROOT}/src/utils/wasi_nn_app_native.c
+)
+target_include_directories(
+  wasi-nn-general
+  PUBLIC
+    ${WASI_NN_ROOT}/include
+    ${WASI_NN_ROOT}/src
+    ${WASI_NN_ROOT}/src/utils
+)
+target_link_libraries(
+  wasi-nn-general
+  PUBLIC
+    libiwasm
+)
+target_compile_definitions(
+  wasi-nn-general
+  PUBLIC
+   $<$<CONFIG:Debug>:NN_LOG_LEVEL=0>
+   $<$<CONFIG:Release>:NN_LOG_LEVEL=2>
 )
 
-set (WASI_NN_LIBS tensorflow-lite)
+#
+# wasi-nn backends
+add_library(
+  wasi-nn-tflite
+  SHARED
+    ${WASI_NN_ROOT}/src/wasi_nn_tensorflowlite.cpp
+)
+#target_link_options(
+#  wasi-nn-tflite
+#  PRIVATE
+#    -Wl,--whole-archive libwasi-nn-general.a
+#    -Wl,--no-whole-archive
+#)
+target_link_libraries(
+  wasi-nn-tflite
+  PUBLIC
+    tensorflow-lite
+    wasi-nn-general
+)