fetchPnpmDeps: allow passing existing derivation args
Previously, users had to add hacks to add additional nativeBuildInputs
entries to the fetcher. This way we allow users to append
nativeBuildInputs, impureEnvVars and also merge potential passthru
attributes.
This might cause rebuilds.
Signed-off-by: Sefa Eyeoglu <contact@scrumplex.net>
(cherry picked from commit 63cdea53595d89771ea544783ef89dbeb414094b)