Append .exe to the executable on OS/2

Change-Id: I1c3b17450b08d2fdfacb7b94055da29d4d20f9c8
diff --git a/libs.mk b/libs.mk
index 83e8fea..872a16b 100644
--- a/libs.mk
+++ b/libs.mk
@@ -377,7 +377,7 @@
 
 include $(SRC_PATH_BARE)/test/test.mk
 LIBVPX_TEST_SRCS=$(addprefix test/,$(call enabled,LIBVPX_TEST_SRCS))
-LIBVPX_TEST_BINS=./test_libvpx
+LIBVPX_TEST_BINS=./test_libvpx$(EXE_SFX)
 LIBVPX_TEST_DATA=$(addprefix $(LIBVPX_TEST_DATA_PATH)/,\
                      $(call enabled,LIBVPX_TEST_DATA))
 libvpx_test_data_url=http://downloads.webmproject.org/test_data/libvpx/$(1)