CMake searches include files in system directories first - c++

Question

I have a library that uses CMake as a building system. It builds for ubuntu, but not for windows.
The issue happens because on windows it searches 'Math.h' in system directories first, but not in the project's 'include' directory.
I've tried to rename all 'Math' files and class by 'Math2' and it works great. But I don't want to rename the class and files.
What do I have to do?
CMakeLists.txt:
cmake_minimum_required (VERSION 3.10)
project (Bint
VERSION "0.1.0"
DESCRIPTION "Bint is an arbitrary-precision arithmetic library."
LANGUAGES CXX
)
enable_testing()
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_EXTENSIONS OFF)
if(MSVC)
#add_compile_options(/Wall)
else()
add_compile_options(-Wall -Wextra -pedantic)
endif()
include_directories(BEFORE ./include)
set(BINT_SRC src/Bint.cpp)
set(MATH_SRC src/Math.cpp)
add_library(shareobjects OBJECT ${BINT_SRC} ${MATH_SRC})
add_executable(test-main-fast tests/main.cpp ${BINT_SRC} ${MATH_SRC})
set_target_properties(test-main-fast PROPERTIES COMPILE_FLAGS -Ofast)
add_test(NAME tst-main-fast COMMAND ./test-main-fast)
aux_source_directory(tests TESTS)
foreach(tstfile ${TESTS})
string(REGEX MATCH "\/(.*)\\.[^.]*$" dummy ${tstfile})
add_executable(test-${CMAKE_MATCH_1} ${tstfile} $<TARGET_OBJECTS:shareobjects>)
add_test(NAME tst-${CMAKE_MATCH_1} COMMAND ./test-${CMAKE_MATCH_1})
endforeach()
add_library(Bint SHARED ${BINT_SRC} ${MATH_SRC})
set_target_properties(test-main-fast PROPERTIES COMPILE_FLAGS -Ofast)
add_library(Bint_static STATIC $<TARGET_OBJECTS:shareobjects>)
set_target_properties(Bint_static PROPERTIES OUTPUT_NAME Bint)