llvm-nm command line too long on windows with 2.0.15 for big link line

[jpharvey]

I am getting an error linking a library with 2.0.15 which didnt happen with 2.0.13
File "d:\compilers\emscripten-2.0.15\upstream\emscripten\em++.py", line 14, in
sys.exit(emcc.run(sys.argv))
File "d:\compilers\emscripten-2.0.15\upstream\emscripten\emcc.py", line 2105, in run
extra_files_to_link += system_libs.calculate([f for _, f in sorted(temp_files)] + extra_files_to_link, link_as_cxx, forced=forced_stdlibs)
File "d:\compilers\emscripten-2.0.15\upstream\emscripten\tools\system_libs.py", line 1422, in calculate
handle_reverse_deps(input_files)
File "d:\compilers\emscripten-2.0.15\upstream\emscripten\tools\system_libs.py", line 1390, in handle_reverse_deps
symbolses = building.llvm_nm_multiple([os.path.abspath(t) for t in input_files])
File "d:\compilers\emscripten-2.0.15\upstream\emscripten\tools\building.py", line 379, in llvm_nm_multiple
results = run_process(cmd, stdout=PIPE, stderr=PIPE, check=False)
File "d:\compilers\emscripten-2.0.15\upstream\emscripten\tools\shared.py", line 96, in run_process
ret = subprocess.run(cmd, check=check, input=input, *args, **kw)
File "D:\obj\windows-release\37amd64_Release\msi_python\zip_amd64\subprocess.py", line 472, in run
File "D:\obj\windows-release\37amd64_Release\msi_python\zip_amd64\subprocess.py", line 775, in init
File "D:\obj\windows-release\37amd64_Release\msi_python\zip_amd64\subprocess.py", line 1178, in _execute_child
FileNotFoundError: [WinError 206] The filename or extension is too long

I am linking a lot of files via a redirect file and i believe the command line is too long.
Previously before #13465 llvm-nm was run per file. now all the files are passed to it on the command line.
I suspect that the fix is to use a redirect file for running this which i believe llvm-nm supports.

[kripken]

This may be fixed by #13664 but I don't have a windows machine to test on - can you please verify @jpharvey ?

[jpharvey]

Confirmed this fixes the problem. Thankyou