[clang-win] invalid assembler invocation

Jamroot:
`exe main : main.asm ;`

main.asm:
`empty`

command line:
`b2.exe toolset=clang-win -sBOOST_ROOT=C:\path\to\boost`

error:
clang-win.compile.asm bin\clang-vc14-win\debug\main.obj
'-c' is not recognized as an internal or external command,
operable program or batch file.
-c -Zp4 -Cp -Cx /Zi /Zd /W3 -Fo "bin\clang-vc14-win\debug\main.obj" "main.asm"
...failed clang-win.compile.asm bin\clang-vc14-win\debug\main.obj...

As you can see, ml.exe (or ml64.exe for address-model=64) is missing in command line.