tidedb: fix libcxx builds

libcxx (as of llvm-19) does not yet support `stop_token` and `jthread`
without the -fexperimental-library flag. Tidedb adds its own
implementations in the std namespace which conflict with libcxx.  This
test can be re-enabled once libcxx supports stop_token and jthread.

https://hydra.nixos.org/build/281874632
https://cache.nixos.org/log/60fzb06ivb7cf4bx4f3varzib1wdyy5z-tiledb-2.18.2.drv

pkgs/by-name/ti/tiledb/package.nix

@@ -57,6 +57,13 @@ stdenv.mkDerivation rec {
     # add openssl on path
     sed -i '49i list(APPEND OPENSSL_PATHS "${openssl.dev}" "${openssl.out}")' \
       cmake/Modules/FindOpenSSL_EP.cmake
+  ''
+    # libcxx (as of llvm-19) does not yet support `stop_token` and `jthread`
+    # without the -fexperimental-library flag. Tidedb adds its own
+    # implementations in the std namespace which conflict with libcxx. This
+    # test can be re-enabled once libcxx supports stop_token and jthread.
+    + lib.optionalString (stdenv.cc.libcxx != null) ''
+    truncate -s0 tiledb/stdx/test/CMakeLists.txt
   '';
 
   # upstream will hopefully fix this in some newer release