THRIFT-3949 missing make dist entry for compiler/cpp/test

This closes #1115
diff --git a/compiler/cpp/Makefile.am b/compiler/cpp/Makefile.am
index caf9424..a239391 100644
--- a/compiler/cpp/Makefile.am
+++ b/compiler/cpp/Makefile.am
@@ -191,6 +191,7 @@
              coding_standards.md \
              README.md \
              CMakeLists.txt \
+             test \
              $(WINDOWS_DIST)
 
 clean-local: