Add excludeGlobs option to set exclude glob patterns for autopack

[kylewlacy]

This PR adds a new excludeGlobs option to the autopack config schema (it cannot be used with the paths option, just like the normal globs option). When set, any files that match an excluded pattern will be skipped, even if it matches a pattern from globs

The main use-case is when you have one or more specific paths that should be excluded. In std.toolchain(), we don't want libc.so.6 to get autopacked, even though every other library under lib/ to get autopacked