build-linux: build iommu tools in linux

User-space driver for smmu test engine lies in tools directory.
Build these iommu tools to get user-space smmute driver and test
binary.

Signed-off-by: Vivek Gautam <vivek.gautam@arm.com>
Change-Id: I12d7a9617323cf029fac7d1959094e90116e6800