fix: Don't add additional depend mode options after Clang -- option

fix: Don't add additional depend mode options after Clang -- option

With the depend mode enabled, ccache executes the original command line
verbatim, potentially with the addition of a few extra options. However,
for clang or clang-cl it is not possible to simply append the additional
options to the end of the original command line since there may be a
"--" option to indicate the end of options.

Fix this by inserting the additional options directly after the compiler
instead of at the end.

Fixes #1273.