tests: Build test cases with their respective c++ files

Tested:
    Unit tests still build and pass as expected.

Change-Id: I20b117dcc07c5338ca300303c52df04f3a0e3ff1
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/.gitignore b/.gitignore
index b990003..324af30 100644
--- a/.gitignore
+++ b/.gitignore
@@ -45,4 +45,4 @@
 /test/chip
 /test/event
 /test/handle
-/test/internal_fd
+/test/internal/fd