The merge diff tests were using some common LLB state objects across
multiple test cases, which each have their own buildkit client and ran
in parallel. The LLB client library does not appear to currently work
with such use cases where LLB states are shared, with errors about
concurrent map writes to marshal state constraints occasionally being
hit during test runs.
Until that issue is addressed (or it's made explicit that the LLB client
library is not expected to work in such a way), this works around the
problem by not sharing states and instead using common funcs that return
distinct state instances.
Signed-off-by: Erik Sipsma <erik@sipsma.dev>
21d6b1258f