pkg: allow the omission of the --filter argument

[david-vankampen]

This will allow the explicit omission of the --filter argument in the case of git servers that do not support filtering (reduces warnings on output)

Contribution description

If you provide a definition for the variable NO_GIT_FILTERING, then the --filter=blob:none argument to the git fetch operation will be omitted. This helps clean up occurrences of this message on build: warning: filtering not recognized by server, ignoring which makes the build output cleaner. I briefly perused git documentation to see if there is a way to test if the server supports filtering, but did not find anything, so I opted to allow the user to specify this on their own, if desired.

Testing procedure

I built with and without a definition of NO_GIT_FILTERING. The message warning: filtering not recognized by server, ignoring shows up in the log when it is NOT defined, and does not show up when it IS defined (in both cases I cleared out build/pkg to ensure it was doing a full fetch).

Issues/PRs references

N/A