Added missing file to Makefile.am.

Makefile.am

@@ -1027,6 +1027,7 @@ EXTRA_DIST = $(@DIST_LANG@_EXTRA_DIST)   \
   WORKSPACE                              \
   cmake/CMakeLists.txt                   \
   cmake/README.md                        \
+  cmake/conformance.cmake                   \
   cmake/examples.cmake                   \
   cmake/extract_includes.bat.in          \
   cmake/install.cmake                    \