Use to-upper function instead of $(shell tr)

Calling $(shell tr) ~300 times to convert host to HOST and target to
TARGET was taking 600ms.  Use the to-upper function from
build/make/core/definitions.mk instead.

Bug: 26275726
Test: no change to out/build-hikey960-test-art.ninja
Change-Id: I591a95a5b8348240e1b02f14f302a4835910ec72
1 file changed