sccache doesn't handle invoking unknown commands

[farre]

% ~/.mozbuild/sccache/sccache ls
sccache: error: failed to execute compile
sccache: caused by: Compiler not supported: "/usr/bin/ls: invalid option -- \'E\'\nTry \'/usr/bin/ls --help\' for more information.\n"

See: https://phabricator.services.mozilla.com/D290809#10088441