chmod may not be available on a Windows self-hosted runner

[mcafaro]

We currently assume chmod is available on Windows runners here (and possibly elsewhere):

setup-matlab/src/matlab.ts

Line 128 in 4e2bf2a

const exitCode = await exec.exec(`chmod +x ${path.join(cachedPath, 'matlab-batch'+matlabBatchExt)}`);

It's unlikely that Windows self-hosted runners have chmod and chmod may not even be necessary to run before executing binaries on Windows.