Windows not able to find FLEX_LIBRARIES - c++

Question

When using this CMakeLists.txt
cmake_minimum_required(VERSION 3.17)
project(project_c)
set(CMAKE_CXX_STANDARD 11)
set(project_name project_c)
find_package(BISON)
find_package(FLEX)
BISON_TARGET(parser parser.y ${CMAKE_SOURCE_DIR}/parser.cpp)
FLEX_TARGET(lexer lexer.l ${CMAKE_SOURCE_DIR}/lexer.cpp)
ADD_FLEX_BISON_DEPENDENCY(lexer parser)
add_executable(${project_name} ${BISON_parser_OUTPUTS} ${FLEX_lexer_OUTPUTS})
target_include_directories(${project_name} PRIVATE "${CMAKE_CURRENT_BINARY_DIR}")
target_link_libraries(${project_name} ${FLEX_LIBRARIES})
CMake complains about
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
FL_LIBRARY (ADVANCED)
linked by target "project_c" in directory D:/asant/workspace/CLionProjects/project_c
I've tried to copy the winflex folder inside the project folder but that won't help anyway. This proposed solution isn't working.
This is the complete CMake log
"C:\Program Files\JetBrains\CLion 2018.3.4\bin\cmake\win\bin\cmake.exe" -DCMAKE_BUILD_TYPE=Debug -G "CodeBlocks - MinGW Makefiles" D:\asant\workspace\CLionProjects\project_c
-- The C compiler identification is GNU 8.1.0
-- The CXX compiler identification is GNU 8.1.0
-- Check for working C compiler: C:/Qt/Tools/mingw810_64/bin/gcc.exe
-- Check for working C compiler: C:/Qt/Tools/mingw810_64/bin/gcc.exe - works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: C:/Qt/Tools/mingw810_64/bin/g++.exe
-- Check for working CXX compiler: C:/Qt/Tools/mingw810_64/bin/g++.exe - works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found BISON: C:/Program Files (x86)/win_flex_bison-2.5.23/win_bison.exe (found version "3.7.1")
-- Found FLEX: C:/Program Files (x86)/win_flex_bison-2.5.23/win_flex.exe (found version "2.6.4")
-- Configuring done
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
FL_LIBRARY (ADVANCED)
linked by target "project_c" in directory D:/asant/workspace/CLionProjects/project_c
-- Generating done
CMake Generate step failed. Build files cannot be regenerated correctly.
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