Use -target-feature for MTE

Instead of setting -march, use clang's -target-feature functionality
to enable MTE. Some projects set -march which may conflict with MTE's
usage. Using -target-feature to enable MTE removes any clang command
line ordering issues.

History:
* Originally submitted as 94d296d3
* reverted in b77d695f due to
  bug 371029823
* Prematurely resubmitted as 0feac37f
  and then subsequently reverted in
  159860c8 as the fix for bug 371029823
  had not yet landed.
* Reapplied as eba30c35 and
  subsequently reverted in 3f685cd5
  due to bug 399925046 (build timeout issue), which was resolved in
  bug 401292715 (re-client upgrade).

Let's try again. 4th time's the charm.

Bug: 366222162
Test: compiles and boots
Change-Id: Ied4606b96cb2967af8edcbb4184981e09c807564