From 1f1767f5afbbb963d9a3de14c977ea5b5b0adc5d Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Wed, 29 Jul 2020 17:36:34 -0400
Subject: [PATCH] convert linker choice to (advanced) choice. only for Clang
 and GNU at the moment

---
 cmake/Modules/Testing.cmake | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/cmake/Modules/Testing.cmake b/cmake/Modules/Testing.cmake
index 3207bc4b3b..29f8b61802 100644
--- a/cmake/Modules/Testing.cmake
+++ b/cmake/Modules/Testing.cmake
@@ -16,15 +16,30 @@ if(ENABLE_TESTING)
   set(MEMORYCHECK_COMMAND "${VALGRIND_BINARY}" CACHE FILEPATH "Memory Check Command")
   set(MEMORYCHECK_COMMAND_OPTIONS "${VALGRIND_DEFAULT_OPTIONS}" CACHE STRING "Memory Check Command Options")
 
-  # check if a faster linker is available
+  # check if a faster linker is available.
+  # only verified with GNU and Clang compilers and new CMake
   if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.13)
-    include(CheckCXXCompilerFlag)
-    check_cxx_compiler_flag(-fuse-ld=lld HAVE_LLD_LINKER)
-    check_cxx_compiler_flag(-fuse-ld=gold HAVE_GOLD_LINKER)
-    if(HAVE_LLD_LINKER)
-      target_link_options(lammps PUBLIC -fuse-ld=lld)
-    elseif(HAVE_GOLD_LINKER)
-      target_link_options(lammps PUBLIC -fuse-ld=gold)
+    if((${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU")
+        OR (${CMAKE_CXX_COMPILER_ID} STREQUAL "Clang"))
+      include(CheckCXXCompilerFlag)
+      set(CMAKE_CUSTOM_LINKER_DEFAULT default)
+      check_cxx_compiler_flag(-fuse-ld=lld HAVE_LLD_LINKER)
+      check_cxx_compiler_flag(-fuse-ld=gold HAVE_GOLD_LINKER)
+      check_cxx_compiler_flag(-fuse-ld=bfd HAVE_BFD_LINKER)
+      if(HAVE_LLD_LINKER)
+        set(CMAKE_CUSTOM_LINKER_DEFAULT lld)
+      elseif(HAVE_GOLD_LINKER)
+        set(CMAKE_CUSTOM_LINKER_DEFAULT gold)
+      elseif(HAVE_BFD_LINKER)
+        set(CMAKE_CUSTOM_LINKER_DEFAULT bfd)
+      endif()
+      set(CMAKE_CUSTOM_LINKER_VALUES lld gold bfd default)
+      set(CMAKE_CUSTOM_LINKER ${CMAKE_CUSTOM_LINKER_DEFAULT} CACHE STRING "Choose a custom linker for faster linking (lld, gold, bfd, default)")
+      validate_option(CMAKE_CUSTOM_LINKER CMAKE_CUSTOM_LINKER_VALUES)
+      mark_as_advanced(CMAKE_CUSTOM_LINKER)
+      if(NOT "${CMAKE_CUSTOM_LINKER}" STREQUAL "default")
+        target_link_options(lammps PUBLIC -fuse-ld=${CMAKE_CUSTOM_LINKER})
+      endif()
     endif()
   endif()