[libc] Add an off-by-default option to silence "skipping" messages from CMake.

libc/CMakeLists.txt

 
 if(LLVM_ENABLE_RUNTIMES AND NOT LLVM_RUNTIMES_BUILD)
   # When libc is build as part of the runtimes/bootstrap build's CMake run, we
   # only need to build the host tools to build the libc. So, we just do enough
   # to build libc-hdrgen and return.
   return()
 endif()
 
+option(LIBC_CMAKE_VERBOSE_LOGGING
+       "Log details warnings and notifications during CMake configuration." OFF)
 # Path libc/scripts directory.
 set(LIBC_BUILD_SCRIPTS_DIR "${LIBC_SOURCE_DIR}/utils/build_scripts")
 
 # Flags to pass down to the compiler while building the libc functions.
 set(LIBC_COMPILE_OPTIONS_DEFAULT "" CACHE STRING "Architecture to tell clang to optimize for (e.g. -march=... or -mcpu=...)")
 
 include(common_libc_tuners.cmake)
 

libc/cmake/modules/LLVMLibCObjectRules.cmake

set_target_properties(
       PROPERTIES
         "ENTRYPOINT_NAME" ${ADD_ENTRYPOINT_OBJ_NAME}
         "TARGET_TYPE" ${ENTRYPOINT_OBJ_TARGET_TYPE}
         "OBJECT_FILE" ""
         "OBJECT_FILE_RAW" ""
         "DEPS" ""
         "SKIPPED" "YES"
     )
+    if(LIBC_CMAKE_VERBOSE_LOGGING)
       message(STATUS "Skipping libc entrypoint ${fq_target_name}.")
+    endif()
     return()
   endif()
 
   if(ADD_ENTRYPOINT_OBJ_ALIAS)
     # Alias targets help one add aliases to other entrypoint object targets.
     # One can use alias targets setup OS/machine independent entrypoint targets.
     list(LENGTH ADD_ENTRYPOINT_OBJ_DEPENDS deps_size)
     if(NOT (${deps_size} EQUAL "1"))

libc/cmake/modules/LLVMLibCTestRules.cmake

if(skipped_entrypoints_list)
     # the libc and it is assumed that they will be rare in practice. So, they
     # can be skipped in the corresponding CMake files using platform specific
     # logic. This pattern is followed in the startup tests for example.
     #
     # Another pattern that is present currently is to detect machine
     # capabilities and add entrypoints and tests accordingly. That approach is
     # much lower level approach and is independent of the kind of skipping that
     # is happening here at the entrypoint level.
-
+    if(LIBC_CMAKE_VERBOSE_LOGGING)
       set(msg "Skipping unittest ${fq_target_name} as it has missing deps: "
               "${skipped_entrypoints_list}.")
       message(STATUS ${msg})
+    endif()
     return()
   endif()
 
   if(SHOW_INTERMEDIATE_OBJECTS)
     message(STATUS "Adding unit test ${fq_target_name}")
     if(${SHOW_INTERMEDIATE_OBJECTS} STREQUAL "DEPS")
       foreach(dep IN LISTS ADD_OBJECT_DEPENDS)
         message(STATUS "  ${fq_target_name} depends on ${dep}")
message(FATAL_ERROR "'add_libc_fuzzer' target requires a DEPENDS list of "
                         "'add_entrypoint_object' targets.")
   endif()
 
   get_fq_target_name(${target_name} fq_target_name)
   get_fq_deps_list(fq_deps_list ${LIBC_FUZZER_DEPENDS})
   get_object_files_for_test(
       link_object_files skipped_entrypoints_list ${fq_deps_list})
   if(skipped_entrypoints_list)
+    if(LIBC_CMAKE_VERBOSE_LOGGING)
       set(msg "Skipping fuzzer target ${fq_target_name} as it has missing deps: "
               "${skipped_entrypoints_list}.")
       message(STATUS ${msg})
+    endif()
     add_custom_target(${fq_target_name})
 
     # A post build custom command is used to avoid running the command always.
     add_custom_command(
       TARGET ${fq_target_name}
       POST_BUILD
       COMMAND ${CMAKE_COMMAND} -E echo ${msg}
     )

libc/test/src/math/differential_testing/CMakeLists.txt

message(FATAL_ERROR "'add_diff_binary' target requires a DEPENDS list of "
                         "'add_entrypoint_object' targets.")
   endif()
 
   get_fq_target_name(${target_name} fq_target_name)
   get_fq_deps_list(fq_deps_list ${DIFF_DEPENDS})
   get_object_files_for_test(
       link_object_files skipped_entrypoints_list ${fq_deps_list})
   if(skipped_entrypoints_list)
+    if(LIBC_CMAKE_VERBOSE_LOGGING)
       set(msg "Will not build ${fq_target_name} as it has missing deps: "
               "${skipped_entrypoints_list}.")
       message(STATUS ${msg})
+    endif()
     return()
   endif()
 
   add_executable(
     ${fq_target_name}
     EXCLUDE_FROM_ALL
     ${DIFF_SRCS}
     ${DIFF_HDRS}