[libc++][C++20 modules] Tests no random device build.

[Mordante]

Summary

Depends on D158337

libcxx/cmake/caches/Generic-no-random_device.cmake

+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")

libcxx/docs/Modules.rst

  * Running tests using the ``std`` module
  * Using the ``std`` module in external projects
  * The following "parts disabled" configuration options are supported
 
    * ``LIBCXX_ENABLE_LOCALIZATION``
    * ``LIBCXX_ENABLE_WIDE_CHARACTERS``
    * ``LIBCXX_ENABLE_THREADS``
    * ``LIBCXX_ENABLE_FILESYSTEM``
+   * ``LIBCXX_ENABLE_RANDOM_DEVICE``
 
 Some of the current limitations
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
  * There is no official build system support, libc++ has experimental CMake support
  * Requires CMake 3.26 for C++23 support
  * Requires CMake 3.27 for C++26 support
  * Requires Ninja 1.11

libcxx/modules/CMakeLists.txt.in

macro(compile_define_if_not condition def)
   endif()
 endmacro()
 macro(compile_define_if condition def)
   if (${condition})
     target_compile_definitions(std PRIVATE ${def})
   endif()
 endmacro()
 
-if(NOT @LIBCXX_ENABLE_RANDOM_DEVICE@)
-  message(FATAL_ERROR "Modules without randome device support is not yet implemented.")
-endif()
 if(NOT @LIBCXX_ENABLE_UNICODE@)
   message(FATAL_ERROR "Modules without Unicode support is not yet implemented.")
 endif()
 if(NOT @LIBCXX_ENABLE_EXCEPTIONS@ OR NOT @LIBCXXABI_ENABLE_EXCEPTIONS@)
   message(FATAL_ERROR "Modules without exception support is not yet implemented.")
 endif()
 
 add_library(std)

libcxx/modules/std/random.inc

export namespace std {
   using std::mt19937_64;
   using std::ranlux24;
   using std::ranlux24_base;
   using std::ranlux48;
   using std::ranlux48_base;
 
   using std::default_random_engine;
 
+#ifndef _LIBCPP_HAS_NO_RANDOM_DEVICE
   // [rand.device], class random_device
   using std::random_device;
+#endif
 
   // [rand.util.seedseq], class seed_seq
   using std::seed_seq;
 
   // [rand.util.canonical], function template generate_canonical
   using std::generate_canonical;
 
   // [rand.dist.uni.int], class template uniform_int_distribution

libcxx/utils/ci/buildkite-pipeline.yml

- label: "No filesystem"
       timeout_in_minutes: 120
 
     - label: "No random device"
       command: "libcxx/utils/ci/run-buildbot generic-no-random_device"
       artifact_paths:
         - "**/test-results.xml"
         - "**/*.abilist"
       env:
-          CC: "clang-${LLVM_HEAD_VERSION}"
-          CXX: "clang++-${LLVM_HEAD_VERSION}"
+          # Note: Modules require and absolute path for clang-scan-deps
+          # https://github.com/llvm/llvm-project/issues/61006
+          CC: "/usr/lib/llvm-${LLVM_HEAD_VERSION}/bin/clang"
+          CXX: "/usr/lib/llvm-${LLVM_HEAD_VERSION}/bin/clang++"
+          CMAKE: "/opt/bin/cmake"
           ENABLE_CLANG_TIDY: "On"
       agents:
         queue: "libcxx-builders"
         os: "linux"
       retry:
         automatic:
           - exit_status: -1  # Agent was lost
             limit: 2