Add CONFIG_ACCOUNTING support to the cmake build.

BUG=https://bugs.chromium.org/p/aomedia/issues/detail?id=76

Change-Id: Ia60540f27e2e3d286528f5be3e3d7044e3f615d1
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 554f352..53cc2ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -599,6 +599,17 @@
 set(AOM_UNIT_TEST_INTRIN_SSSE3 "${AOM_ROOT}/test/simd_cmp_ssse3.cc")
 set(AOM_UNIT_TEST_INTRIN_SSE4_1 "${AOM_ROOT}/test/simd_cmp_sse4.cc")
 
+if (CONFIG_ACCOUNTING)
+  set(AOM_AV1_COMMON_SOURCES
+      ${AOM_AV1_COMMON_SOURCES}
+      "${AOM_ROOT}/av1/common/accounting.c"
+      "${AOM_ROOT}/av1/common/accounting.h")
+
+  set(AOM_UNIT_TEST_SOURCES
+      ${AOM_UNIT_TEST_SOURCES}
+      "${AOM_ROOT}/test/accounting_test.cc")
+endif ()
+
 if (CONFIG_CLPF)
   set(AOM_AV1_COMMON_SOURCES
       ${AOM_AV1_COMMON_SOURCES}