Remove test_per_src from build/kati

test_per_src is being removed, it never worked well and is incompatible
with all of the test infrastructure.  Build the kati test binaries
individually.

Test: prebuilts/build-tools/build-prebuilts.sh
Change-Id: I7a51c4a9553897fa2b8273db953d616842b933fc

build/kati

diff --git a/build/kati b/build/kati
index 573ea35..74af332 160000
--- a/build/kati
+++ b/build/kati
@@ -1 +1 @@
-Subproject commit 573ea35b654b77704207551c0439a392e3fc4eb1
+Subproject commit 74af332b81f7b5d631b6b7ffdb870b6340324389