Firefox build error using ./mach build regarding WINDOWSSDKDIR and WINSYSROOT

build-error

$ ./mach build
 0:00.99 W Clobber not needed.
 Config object not found by mach.
 0:01.44 Using Python 3.11.7 from C:\Users\BINIT\.mozbuild\srcdirs\firefox-f55018f8bae5\_virtualenvs
\build\Scripts\python.exe
 0:01.44 checking for vcs source checkout... git
 0:01.50 checking for a shell... C:/mozilla-build/msys2/usr/bin/sh.exe
 0:01.51 checking for host system type... x86_64-pc-windows-msvc
 0:01.51 checking for target system type... x86_64-pc-windows-msvc
 0:01.80 checking whether cross compiling... no
 0:01.90 checking if configuration file confvars.sh exists... D:/mozilla-source/firefox/browser/conf
vars.sh
 0:01.90 checking if configuration file configure.sh exists... D:/mozilla-source/firefox/browser/bra
nding/unofficial/configure.sh
 0:01.92 checking for Python 3... C:/Users/BINIT/.mozbuild/srcdirs/firefox-f55018f8bae5/_virtualenvs
/build/Scripts/python.exe (3.11.7)
 0:01.93 checking for git... C:/Users/BINIT/scoop/shims/git.exe
 0:01.98 checking for Git version... 2.49.0.windows.1
 0:01.98 checking for MozillaBuild directory... C:\mozilla-build\
 0:01.99 checking for MozillaBuild version... 4.1
 0:05.93 checking for wget... C:/mozilla-build/msys2/usr/bin/wget.exe
 0:05.94 checking for ccache... not found
 0:05.94 checking for the target C compiler... C:/Users/BINIT/.mozbuild/clang/bin/clang-cl.exe
 0:06.00 checking whether the target C compiler can be used... yes
 0:06.00 checking the target C compiler version... 19.1.7
 0:06.03 checking the target C compiler works... yes
 0:06.03 checking for the target C++ compiler... C:/Users/BINIT/.mozbuild/clang/bin/clang-cl.exe
 0:06.09 checking whether the target C++ compiler can be used... yes
 0:06.10 checking the target C++ compiler version... 19.1.7
 0:06.13 checking the target C++ compiler works... yes
 0:06.13 checking for the host C compiler... C:/Users/BINIT/.mozbuild/clang/bin/clang-cl.exe
 0:06.13 checking whether the host C compiler can be used... yes
 0:06.13 checking the host C compiler version... 19.1.7
 0:06.13 checking the host C compiler works... yes
 0:06.13 checking for the host C++ compiler... C:/Users/BINIT/.mozbuild/clang/bin/clang-cl.exe
 0:06.13 checking whether the host C++ compiler can be used... yes
 0:06.13 checking the host C++ compiler version... 19.1.7
 0:06.14 checking the host C++ compiler works... yes
 0:06.17 checking for 64-bit OS... yes
 0:06.22 ERROR: WINDOWSSDKDIR cannot be set when using the bootstrapped WINSYSROOT
*** Fix above errors and then restart with "./mach build"

This was because of a rogue environment variable from when I was using Portable Build Tools.