Skip unused TooManyCooks, it requires newer libcxx

Index: cmake/external/CMakeLists.txt
--- cmake/external/CMakeLists.txt.orig
+++ cmake/external/CMakeLists.txt
@@ -49,7 +49,6 @@ add_checked_subdirectory(ranges)
 add_checked_subdirectory(rlottie)
 add_checked_subdirectory(rnnoise)
 add_checked_subdirectory(tde2e)
-add_checked_subdirectory(tmc)
 add_checked_subdirectory(ton)
 add_checked_subdirectory(variant)
 add_checked_subdirectory(vpx)
