As long as you have the RAM available and your OS has reasonable file system caching behavior - you should already get that effect. On Linux, I can run a build

As long as you have the RAM available and your OS has reasonable file system caching behavior - you should already get that effect. On Linux, I can run a build repeatedly that touches several GB of files and there is basically zero IO during the build, because everything is in the page cache. There is some IO at some point after the build as the dirty files (e.g., .o files) get written out, but if if you delete them fast enough, even that doesn't happen.