Point to the linaro toolchain

Change-Id: I62a2f90056615c9e37aaa19ded963e43c4cdf578
Remove calculator compile. we'd use prebuilts.

Change-Id: I6654bf8411a7e2c8b0c0350c31e2d77da1adae30
Revert "Point to the linaro toolchain"

This is causing massive battery drain (?)
so, it's better to revert this, for now.

This reverts commit 06acdb291fc6de8a7e0f4da1b89bf9416b99ae3d.