do not use gold linker by default

We have been detecting the existence of the gold linker and
automatically try to use it. This PR removes this for the following
reasons:
1. gold linker is now deprecated,
https://lists.gnu.org/archive/html/info-gnu/2025-02/msg00001.html
2. it sometimes breaks linking, especially with MPI
3. lld and especially mold are much better

Author: tjhei

cmake/checks/check_02_compiler_features.cmake

@@ -401,8 +401,6 @@ if(NOT CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
     add_flags(DEAL_II_LINKER_FLAGS "-fuse-ld=mold")
   elseif(DEAL_II_COMPILER_HAS_FUSE_LD_LLD)
     add_flags(DEAL_II_LINKER_FLAGS "-fuse-ld=lld")
-  elseif(DEAL_II_COMPILER_HAS_FUSE_LD_GOLD)
-    add_flags(DEAL_II_LINKER_FLAGS "-fuse-ld=gold")
   endif()
 
   reset_cmake_required()

cmake/setup_sanity_checks.cmake

@@ -63,8 +63,6 @@ foreach(build ${DEAL_II_BUILD_TYPES})
     set(_replacement "")
     if(DEAL_II_COMPILER_HAS_FUSE_LD_LLD)
       set(_replacement "-fuse-ld=lld")
-    elseif(DEAL_II_COMPILER_HAS_FUSE_LD_GOLD)
-      set(_replacement "-fuse-ld=gold")
     endif()
     _drop_linker_flag(
       "-fuse-ld=mold" ${_replacement}
@@ -75,9 +73,6 @@ foreach(build ${DEAL_II_BUILD_TYPES})
 
   if(NOT DEAL_II_HAVE_USABLE_FLAGS_${build} AND DEAL_II_COMPILER_HAS_FUSE_LD_LLD)
     set(_replacement "")
-    if(DEAL_II_COMPILER_HAS_FUSE_LD_GOLD)
-      set(_replacement "-fuse-ld=gold")
-    endif()
     _drop_linker_flag(
       "-fuse-ld=lld" ${_replacement}
       DEAL_II_COMPILER_HAS_FUSE_LD_LLD