CMake fatal error LNK1112: module machine type 'x64' conflicts with target machine type 'x86'

I am learning how to use CMake,

I am converting a working project from Visual Studio to Cmake and building with NMake. The current projects builds for both x64 and x86

My current CMakeLists.txt is very simple:

cmake_minimum_required(VERSION 3.13.0)

project(SimManager CXX)

ADD_DEFINITIONS(-DUNICODE)
ADD_DEFINITIONS(-D_UNICODE)

set(CMAKE_CXX_FLAGS -G"NMake Makefiles")

set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_executable(SimManager
    Source/main.cpp
    )

set_target_properties (${PROJECT_NAME} PROPERTIES
    CXX_STANDARD 17
    CXX_STANDARD_REQUIRED TRUE
    CXX_EXTENSIONS FALSE
    )

The error I get is

fatal error LNK1112: module machine type 'x64' conflicts with target machine type 'x86'

I understand the way NMake chooses which compiler to use, x86 or x64, is by opening the appropriate console terminal. I am using Select x64 Native Tools Command Prompt for VS 2017

The command line for the linker that gets executed is:

command "C:\PROGRA~2\MIB055~1\2019\ENTERP~1\VC\Tools\MSVC\1425~1.286\bin\Hostx86\x86\link.exe /nologo @CMakeFiles\SimManager.dir\objects1.rsp /out:SimManager.exe /implib:SimManager.lib /pdb:E:\Projects\SimManager\Debug\SimManager.pdb /version:0.0 /machine:X86 /debug /INCREMENTAL /subsystem:console kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:CMakeFiles\SimManager.dir/intermediate.manifest CMakeFiles\SimManager.dir/manifest.res" failed (exit code 1112) with the following output: fatal error LNK1112: module machine type 'x64' conflicts with target machine type 'x86'

I can see it has /machine:X86 set in it. I am not setting this in CMakeLists.txt. How can I make it use a 64 bit linker?

I tried adding suggested arguments to the cmake call, it did not make a difference cmake -G"NMake Makefiles" --build build64 --config Release -host_arch=amd64 -arch=amd64 ..

Thanks