installer: allow overriding of NIX_FIRST_BUILD_ID on darwin (cherry picked from commit e85fd92816571ea00abafa3929298d0e091bcb9b) Change-Id: Ifffc3fedd740079345c205f54c62c76053e24846
installer: allow overriding of NIX_FIRST_BUILD_ID on darwin (cherry picked from commit e85fd92816571ea00abafa3929298d0e091bcb9b) Change-Id: Ifffc3fedd740079345c205f54c62c76053e24846