Try modifying build.bat

.github/workflows/csharp-tests.yml

@@ -46,19 +46,14 @@ jobs:
             ext: .dll
             reqs:
     steps:
+    - uses: ilammy/msvc-dev-cmd@v1
     - uses: actions/checkout@v3
       with:
         submodules: recursive
     - name: Install requirements
       if: ${{ matrix.target.reqs }}
       run: ${{ matrix.target.reqs }}
-    - name: Build native library for ${{ matrix.target.location }} using native capabilities (windows)
-      if: runner.os == 'windows'
-      shell: cmd
-      run: |
-        "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\Common7\Tools\VsDevCmd.bat" && make ckzg -C bindings/csharp CC=clang EXTENSION=${{ matrix.target.ext }} LOCATION=${{ matrix.target.location }} ARCH=${{ matrix.target.arch }}
-    - name: Build native library for ${{ matrix.target.location }} using native capabilities (not windows)
-      if: runner.os != 'windows'
+    - name: Build native library for ${{ matrix.target.location }} using native capabilities
       run: make ckzg -C bindings/csharp CC=clang EXTENSION=${{matrix.target.ext}} LOCATION=${{matrix.target.location}} ARCH=${{matrix.target.arch}}
     - name: Upload artifacts
       uses: actions/upload-artifact@v3

build.bat

@@ -0,0 +1,53 @@
+@echo off
+SETLOCAL
+set "PATH=%windir%\system32;%PATH%" &:: override msys if there is one on %PATH%
+set TOP=%~dp0
+cl /nologo /c /O2 /Zi /Fdblst.pdb /W4 /MT /Zl %TOP%src\server.c || EXIT /B
+cl 2>&1 | find "for ARM64" > nul:
+IF ERRORLEVEL 1 (
+    set arm64=no
+    FOR %%F IN (%TOP%build\win64\*-x86_64.asm) DO (
+        ml64 /nologo /c /Cp /Cx /Zi %%F || EXIT /B
+    )
+) ELSE (
+    set arm64=yes
+    FOR %%F IN (%TOP%build\win64\*-armv8.asm) DO (
+        armasm64 -nologo %%F || EXIT /B
+    )
+)
+SETLOCAL ENABLEDELAYEDEXPANSION
+set static=/out:blst.lib
+set shared=
+set arm64ec=
+FOR %%O IN (%*) DO (
+    set opt=%%O
+    IF "!opt!" == "-shared" (
+        IF [!shared!] EQU [] set shared=/out:blst.dll
+    ) ELSE IF "!opt:~0,5!" == "/out:" (
+	IF "!opt:~-4!" == ".dll" (set shared=!opt!) ELSE (set static=!opt!)
+    ) ELSE IF "!opt!" == "-arm64x" (
+        set arm64x=%arm64%
+    )
+)
+IF [%shared%] NEQ [] (
+    cl /nologo /c /O2 /Oi- /MD %TOP%build\win64\dll.c || EXIT /B
+    IF [%arm64x%] NEQ [yes] (
+        link /nologo /debug /dll /entry:DllMain /incremental:no %shared% ^
+             /def:%TOP%build\win64\blst.def *.obj kernel32.lib && del *.obj
+    ) ELSE (
+        lib /nologo /out:blst_arm64.lib *.obj && del *.obj || EXIT /B
+        cl /nologo /arm64EC /c /O2 /Zi /Fdblst.pdb /W4 /MT /Zl %TOP%src\server.c || EXIT /B
+        FOR %%F IN (%TOP%build\win64\*-armv8.asm) DO (
+            armasm64 -nologo -machine arm64ec -nowarn %%F || EXIT /B
+        )
+        cl /nologo /arm64EC /c /O2 /Oi- /MD %TOP%build\win64\dll.c || EXIT /B
+        link /nologo /machine:arm64x /dll /noentry %shared% ^
+             /def:%TOP%build\win64\blst.def *.obj ^
+             /defArm64Native:%TOP%build\win64\blst.def blst_arm64.lib ^
+             kernel32.lib && del *.obj blst_arm64.lib
+    )
+) ELSE (
+    lib /nologo %static% *.obj && del *.obj
+)
+ENDLOCAL
+EXIT /B

src/Makefile

@@ -119,6 +119,7 @@ $(BLST_BUILDSCRIPT):
 	@git submodule update --init
 
 $(BLST_LIBRARY): $(BLST_BUILDSCRIPT)
+        @cp ../build.bat ../blst/build.bat
 	@cd $(dir $(BLST_BUILDSCRIPT)) && \
 	./$(notdir $(BLST_BUILDSCRIPT)) $(BLST_BUILDSCRIPT_FLAGS) && \
 	cp $(notdir $(BLST_LIBRARY)) ../lib && \