build: add the circular-buffer unit tests to cargo_test_cantrip

Change-Id: I001f0634a9a972ccf29cf09fd3fc4f1b445ce4e4

cantrip_tests.mk

diff --git a/cantrip_tests.mk b/cantrip_tests.mk
index 6d6a810..c272a0b 100644
--- a/cantrip_tests.mk
+++ b/cantrip_tests.mk
@@ -22,6 +22,7 @@
 #   cargo_test_cantrip_proc_interface; they need to be rewritten (or tossed)
 CARGO_TEST_CANTRIP=\
   cargo_test_cantrip_os_common_slot_allocator \
+  cargo_test_circular_buffer \
   cargo_test_i2s_driver \
   cargo_test_mailbox_driver \
   cargo_test_opentitan_timer \
@@ -49,6 +50,10 @@
 	cd $(CANTRIP_COMPONENTS)/cantrip-os-common/src/slot-allocator && \
 		$(CARGO_TEST) -- --test-threads=1
 
+## Runs cargo unit tests for the cicular-buffer support
+cargo_test_circular_buffer: | cantrip-gen-headers
+	cd $(CANTRIP_COMPONENTS)/UARTDriver/circular-buffer && $(CARGO_TEST)
+
 ## Runs cargo unit tests for the DebugConsole zmomdem support
 cargo_test_debugconsole_zmodem: | cantrip-gen-headers
 	cd $(CANTRIP_COMPONENTS)/DebugConsole/zmodem && $(CARGO_TEST)