Fix incorrect usage of CMAKE_{SOURCE,BINARY}_DIR (#90)

When importing cudnn-frontend as a 3rd party library using FetchContent,
cmake incorrectly parse the file path. This is because we incorrectly using
CMAKE_SOURCE_DIR variable, which should be PROJECT_SOURCE_DIR (The former one
refers to the top-level source directory that contains a CMakeLists.txt, while
the latter refers to the source directory of the most recent project() command

python/CMakeLists.txt

@@ -16,7 +16,7 @@ FetchContent_MakeAvailable(dlpack)
 find_package(Python 3.8 COMPONENTS Interpreter Development.Module REQUIRED)
 
 # Find cudnn
-include(${CMAKE_SOURCE_DIR}/cmake/cuDNN.cmake)
+include(${PROJECT_SOURCE_DIR}/cmake/cuDNN.cmake)
 
 option(CUDNN_FRONTEND_FETCH_PYBINDS_IN_CMAKE "Whether cmake build system should fetch pybinds." ON)
 if(CUDNN_FRONTEND_FETCH_PYBINDS_IN_CMAKE)
@@ -81,7 +81,7 @@ set_target_properties(
         _compiled_module
 
         PROPERTIES
-        LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/cudnn
+        LIBRARY_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/cudnn
     )
-    file(COPY ${CMAKE_SOURCE_DIR}/python/cudnn DESTINATION ${CMAKE_BINARY_DIR})
+    file(COPY ${PROJECT_SOURCE_DIR}/python/cudnn DESTINATION ${PROJECT_BINARY_DIR})
 endif()

samples/CMakeLists.txt

@@ -17,7 +17,7 @@ if(NOT Catch2_FOUND)
 endif()
 
 # Find cudnn
-include(${CMAKE_SOURCE_DIR}/cmake/cuDNN.cmake)
+include(${PROJECT_SOURCE_DIR}/cmake/cuDNN.cmake)
 
 add_executable(
     samples
@@ -107,7 +107,7 @@ set_target_properties(
     samples
     PROPERTIES
     LINK_WHAT_YOU_USE TRUE
-    RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin
+    RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/bin
 )
 
 set_source_files_properties(

test/unit_tests/CMakeLists.txt

@@ -60,5 +60,5 @@ set_target_properties(
     unit_tests
     PROPERTIES
     LINK_WHAT_YOU_USE TRUE
-    RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin
+    RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/bin
 )