Add OWNERS in build/make

* Owners are selected from top CL approvals or owners.
  They will be suggested to review/approve future CLs.
* OWNERS files are recognized by the new find-owners plugin, see .md files in
  https://gerrit.googlesource.com/plugins/find-owners/+/master/src/main/resources/Documentation/

Test: build/make/tools/checkowners.py -c -v OWNERS
Change-Id: Ibe6765e5448c471ca413413e3d052507ccee4ea6
diff --git a/tools/OWNERS b/tools/OWNERS
new file mode 100644
index 0000000..7a23adc
--- /dev/null
+++ b/tools/OWNERS
@@ -0,0 +1,2 @@
+per-file warn.py = chh@google.com
+per-file checkowners.py = chh@google.com
diff --git a/tools/releasetools/OWNERS b/tools/releasetools/OWNERS
new file mode 100644
index 0000000..39448cf
--- /dev/null
+++ b/tools/releasetools/OWNERS
@@ -0,0 +1 @@
+tbao@google.com