pw_build: Fix issue with temp dirs on Mac
pw_build: Fix issue with temp dirs on Mac

Change-Id: Id872ffd09d26bd2b62e866d290ab785c2b45dfab
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/16705
Reviewed-by: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>
Commit-Queue: Rob Mohr <d07614a8a0b466db08f68224f87d738b0f9615cf@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed