Use musl build of n2

We're seeing bugs on the build server only, and previous similar bugs
were caused by issues in the older version of glibc the build server
uses, so try using the musl build of n2 to see if it resolves the
issues.

Bug: 318434287
Test: Presubmits
Change-Id: I416cd77f4dfb4ca04f6dd5b36fa73585a2904b55