BLD: Cut Travis-CI build times by 30-50%
foo
Merge pull request #6218 from y-p/ironcache

BLD: Cut Travis-CI build times by 30-50%
Revert "foo"

This reverts commit 213593cc5e457d60f70786981d7522ff4a752b3c.
BLD: travis limit ccache to 60M
BLD: travis, skip cache upload when no changes