All the previous answers/comments were correct. The weird thing about my case was the symlinks of the libraries in the build
directory were not valid and were not pointing to the right files. The output of ls -lh /home/Warrior/Desktop/pathtracer/oidn/build
was as follow:
total 160K
drwxrwxr-x 4 amir amir 4.0K Feb 4 00:09 apps
-rw-rw-r-- 1 amir amir 19K Feb 4 00:09 CMakeCache.txt
drwxrwxr-x 7 amir amir 4.0K Feb 4 00:09 CMakeFiles
-rw-rw-r-- 1 amir amir 6.5K Feb 4 00:09 cmake_install.cmake
drwxrwxr-x 3 amir amir 4.0K Feb 4 00:09 common
-rw-r--r-- 1 amir amir 3.6K Feb 4 00:09 CPackConfig.cmake
-rw-r--r-- 1 amir amir 4.0K Feb 4 00:09 CPackSourceConfig.cmake
-rw-rw-r-- 1 amir amir 103K Feb 4 00:09 Makefile
drwxrwxr-x 3 amir amir 4.0K Feb 4 00:08 mkl-dnn
-rw-r--r-- 1 amir amir 1.6K Feb 4 00:09 OpenImageDenoiseConfigVersion.cmake
But when I would go to the directory I would see the following:

What I did was instead of cloning the oidn repo somewhere else and building it, I cloned the oidn repo in /home/Warrior/Desktop/pathtracer/
and built it there. After that I could see the correct file names/symlinks via ls -lh
as follow. Now my program compiles and things work fine. I just had to use LIBS += -L"oidn/build/" -lOpenImageDenoise
when compiling my code:
total 51M
drwxrwxr-x 4 amir amir 4.0K Feb 9 10:14 apps
-rw-rw-r-- 1 amir amir 19K Feb 9 10:14 CMakeCache.txt
drwxrwxr-x 7 amir amir 4.0K Feb 9 10:19 CMakeFiles
-rw-rw-r-- 1 amir amir 5.6K Feb 9 10:14 cmake_install.cmake
-rw-rw-r-- 1 amir amir 2.5K Feb 9 10:17 color_ispc_avx2.h
-rw-rw-r-- 1 amir amir 2.5K Feb 9 10:17 color_ispc_avx512skx.h
-rw-rw-r-- 1 amir amir 3.1K Feb 9 10:17 color_ispc.h
-rw-rw-r-- 1 amir amir 2.5K Feb 9 10:17 color_ispc_sse4.h
drwxrwxr-x 3 amir amir 4.0K Feb 9 10:14 common
-rw-r--r-- 1 amir amir 3.3K Feb 9 10:14 CPackConfig.cmake
-rw-r--r-- 1 amir amir 3.7K Feb 9 10:14 CPackSourceConfig.cmake
-rw-rw-r-- 1 amir amir 2.6K Feb 9 10:17 input_reorder_ispc_avx2.h
-rw-rw-r-- 1 amir amir 2.6K Feb 9 10:17 input_reorder_ispc_avx512skx.h
-rw-rw-r-- 1 amir amir 3.1K Feb 9 10:17 input_reorder_ispc.h
-rw-rw-r-- 1 amir amir 2.6K Feb 9 10:17 input_reorder_ispc_sse4.h
-rw-rw-r-- 1 amir amir 41K Feb 9 10:14 libcommon.a
-rw-rw-r-- 1 amir amir 16M Feb 9 10:17 libdnnl.a
lrwxrwxrwx 1 amir amir 24 Feb 9 10:19 libOpenImageDenoise.so -> libOpenImageDenoise.so.0
lrwxrwxrwx 1 amir amir 28 Feb 9 10:19 libOpenImageDenoise.so.0 -> libOpenImageDenoise.so.1.3.0
-rwxrwxr-x 1 amir amir 34M Feb 9 10:19 libOpenImageDenoise.so.1.3.0
-rw-rw-r-- 1 amir amir 37K Feb 9 10:19 libutils.a
drwxrwxr-x 2 amir amir 4.0K Feb 9 10:17 local__core
-rw-rw-r-- 1 amir amir 104K Feb 9 10:14 Makefile
drwxrwxr-x 3 amir amir 4.0K Feb 9 10:14 mkl-dnn
-rwxrwxr-x 1 amir amir 181K Feb 9 10:19 oidnBenchmark
-rwxrwxr-x 1 amir amir 59K Feb 9 10:19 oidnDenoise
-rwxrwxr-x 1 amir amir 882K Feb 9 10:19 oidnTest
-rw-r--r-- 1 amir amir 1.6K Feb 9 10:14 OpenImageDenoiseConfigVersion.cmake
-rw-rw-r-- 1 amir amir 1.5K Feb 9 10:17 output_copy_ispc_avx2.h
-rw-rw-r-- 1 amir amir 1.5K Feb 9 10:17 output_copy_ispc_avx512skx.h
-rw-rw-r-- 1 amir amir 1.9K Feb 9 10:17 output_copy_ispc.h
-rw-rw-r-- 1 amir amir 1.5K Feb 9 10:17 output_copy_ispc_sse4.h
-rw-rw-r-- 1 amir amir 2.5K Feb 9 10:17 output_reorder_ispc_avx2.h
-rw-rw-r-- 1 amir amir 2.5K Feb 9 10:17 output_reorder_ispc_avx512skx.h
-rw-rw-r-- 1 amir amir 3.1K Feb 9 10:17 output_reorder_ispc.h
-rw-rw-r-- 1 amir amir 2.5K Feb 9 10:17 output_reorder_ispc_sse4.h
-rw-rw-r-- 1 amir amir 1.5K Feb 9 10:17 upsample_ispc_avx2.h
-rw-rw-r-- 1 amir amir 1.5K Feb 9 10:17 upsample_ispc_avx512skx.h
-rw-rw-r-- 1 amir amir 1.8K Feb 9 10:17 upsample_ispc.h
-rw-rw-r-- 1 amir amir 1.5K Feb 9 10:17 upsample_ispc_sse4.h
drwxrwxr-x 2 amir amir 4.0K Feb 9 10:17 weights