Clean up libtorchaudio customization logic (#2039)

Summary:
(See https://github.com/pytorch/audio/issues/2038 description for the overall goal.)
This PR cleans up CMake customization logic for `libtorchaudio`.

It introduces base variables LIBTORCHAUDIO_INCLUDE_DIRS,
LIBTORCHAUDIO_LINK_LIBRARIES and LIBTORCHAUDIO_COMPILE_DEFINITIONS,
which are respectively used when calling `target_include_directories`,
`target_link_libraries` and `target_compile_definitions`.

The customization logic only modifies these variables.

The original implementation called these functions multiple times
(once par customization logic) and it is getting difficult to understand
the customization logic.

Pull Request resolved: https://github.com/pytorch/audio/pull/2039

Reviewed By: carolineechen, nateanl

Differential Revision: D32683004

Pulled By: mthrok

fbshipit-source-id: 4d41f21692ac139b1185a6ab69eb45d881ee7e73

torchaudio/csrc/CMakeLists.txt

@@ -10,6 +10,23 @@ set(
   utils.cpp
   )
 
+set(
+  LIBTORCHAUDIO_INCLUDE_DIRS
+  ${PROJECT_SOURCE_DIR}
+  )
+
+set(
+  LIBTORCHAUDIO_LINK_LIBRARIES
+  torch
+  ${TORCHAUDIO_THIRD_PARTIES}
+  )
+
+set(
+  LIBTORCHAUDIO_COMPILE_DEFINITIONS)
+
+#------------------------------------------------------------------------------#
+# START OF CUSTOMIZATION LOGICS
+#------------------------------------------------------------------------------#
 if(BUILD_RNNT)
   list(
     APPEND
@@ -33,8 +50,28 @@ if(BUILD_RNNT)
   endif()
 endif()
 
+if(USE_CUDA)
+  list(
+    APPEND
+    LIBTORCHAUDIO_INCLUDE_DIRS
+    ${CUDA_TOOLKIT_INCLUDE}
+    )
+  list(
+    APPEND
+    LIBTORCHAUDIO_LINK_LIBRARIES
+    ${C10_CUDA_LIBRARY}
+    ${CUDA_CUDART_LIBRARY}
+    )
+  list(
+    APPEND
+    LIBTORCHAUDIO_COMPILE_DEFINITIONS
+    USE_CUDA
+  )
+endif()
+
 if(BUILD_KALDI)
   list(APPEND LIBTORCHAUDIO_SOURCES kaldi.cpp)
+  list(APPEND LIBTORCHAUDIO_COMPILE_DEFINITIONS INCLUDE_KALDI)
 endif()
 
 if(BUILD_SOX)
@@ -47,8 +84,24 @@ if(BUILD_SOX)
     sox/effects_chain.cpp
     sox/types.cpp
     )
+  list(
+    APPEND
+    LIBTORCHAUDIO_COMPILE_DEFINITIONS
+    INCLUDE_SOX
+    )
+endif()
+
+if(OpenMP_CXX_FOUND)
+  list(
+    APPEND
+    LIBTORCHAUDIO_LINK_LIBRARIES
+    OpenMP::OpenMP_CXX
+    )
 endif()
 
+#------------------------------------------------------------------------------#
+# END OF CUSTOMIZATION LOGICS
+#------------------------------------------------------------------------------#
 add_library(
   libtorchaudio
   SHARED
@@ -59,45 +112,21 @@ set_target_properties(libtorchaudio PROPERTIES PREFIX "")
 target_include_directories(
   libtorchaudio
   PRIVATE
-  ${PROJECT_SOURCE_DIR}
+  ${LIBTORCHAUDIO_INCLUDE_DIRS}
   )
-
 target_link_libraries(
   libtorchaudio
-  torch
-  ${TORCHAUDIO_THIRD_PARTIES}
+  ${LIBTORCHAUDIO_LINK_LIBRARIES}
+  )
+target_compile_definitions(
+  libtorchaudio
+  PRIVATE ${LIBTORCHAUDIO_COMPILE_DEFINITIONS}
   )
-
-if (BUILD_SOX)
-  target_compile_definitions(libtorchaudio PUBLIC INCLUDE_SOX)
-endif()
-
-if (BUILD_KALDI)
-  target_compile_definitions(libtorchaudio PUBLIC INCLUDE_KALDI)
-endif()
-
-if(USE_CUDA)
-  target_compile_definitions(libtorchaudio PRIVATE USE_CUDA)
-  target_include_directories(
-    libtorchaudio
-    PRIVATE
-    ${CUDA_TOOLKIT_INCLUDE}
-    )
-  target_link_libraries(
-    libtorchaudio
-    ${C10_CUDA_LIBRARY}
-    ${CUDA_CUDART_LIBRARY}
-    )
-endif()
 
 if (MSVC)
     set_target_properties(libtorchaudio PROPERTIES SUFFIX ".pyd")
 endif(MSVC)
 
-if(OpenMP_CXX_FOUND)
-  target_link_libraries(libtorchaudio OpenMP::OpenMP_CXX)
-endif()
-
 install(
   TARGETS libtorchaudio
   LIBRARY DESTINATION lib
@@ -134,6 +163,11 @@ if (BUILD_TORCHAUDIO_PYTHON_EXTENSION)
     ${EXTENSION_SOURCES}
     )
 
+  target_compile_definitions(
+    _torchaudio
+    PRIVATE ${LIBTORCHAUDIO_COMPILE_DEFINITIONS}
+    )
+
   set_target_properties(_torchaudio PROPERTIES PREFIX "")
   if (MSVC)
     set_target_properties(_torchaudio PROPERTIES SUFFIX ".pyd")