Build Ninja with Soong

With this, our prebuilt version of ninja doesn't rely on random host gcc
/ headers / libstdc++. Instead, it'll use the same checked in clang,
sysroot, and built libc++ as our other host tools. This should make the
ninja builds reproducible.

Change-Id: I8d0ccbabaf065ecc95f41361bb54076f7bdab548
1 file changed
tree: 4e29b6f1b40627e4727c72fa5417fabf7e21cea9