Refactor OWNERS files in platform/build/soong.

Pulls out all of the per-file rules into their relevant directories
so platform/build/soong:/OWNERS can be included everywhere we need
the list of build system owners.

Test: treehugger
Bug: 170407947
Change-Id: I5a4b2d252bd9b3c280cd9954cf0e65ac21153ede
diff --git a/cc/config/OWNERS b/cc/config/OWNERS
index b2f54e5..701db92 100644
--- a/cc/config/OWNERS
+++ b/cc/config/OWNERS
@@ -1 +1,3 @@
 per-file vndk.go = smoreland@google.com, victoryang@google.com
+per-file clang.go,global.go = srhines@google.com, chh@google.com, pirama@google.com, yikong@google.com
+