How do I run a systemCommand in a temp directory while caching the results? (opens in new tab)

I currently am building GMP statically for my project using the provided configure script with addSystemCommand (technically with a bash script to move the header and artifact into addOutputFileArg and addOutputDirectoryArg respectively). This leaves behind a host of .o files and other stuff, and currently I am using setCwd to build in a subdirectory of the GMP zig-pkg path. It seems more idiomatic to me to get a temp path with tmpPath, but when I do so this step no longer caches and re-runs ...