cmake: Add TryAppendLinkerFlag module

Author: hebasto

cmake/module/TryAppendLinkerFlag.cmake

@@ -0,0 +1,80 @@
+# Copyright (c) 2023-present The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or https://opensource.org/license/mit/.
+
+include_guard(GLOBAL)
+include(CheckCXXSourceCompiles)
+
+#[=[
+Usage example:
+
+  try_append_linker_flag(core "-Wl,--major-subsystem-version,6")
+
+
+In configuration output, this function prints a string by the following pattern:
+
+  -- Performing Test LINKER_SUPPORTS_[flag]
+  -- Performing Test LINKER_SUPPORTS_[flag] - Success
+
+]=]
+function(try_append_linker_flag target flag)
+  cmake_parse_arguments(PARSE_ARGV 2
+    TALF                              # prefix
+    ""                                # options
+    "SOURCE;RESULT_VAR"               # one_value_keywords
+    "IF_CHECK_PASSED;IF_CHECK_FAILED" # multi_value_keywords
+  )
+
+  string(MAKE_C_IDENTIFIER "${flag}" result)
+  string(TOUPPER "${result}" result)
+  set(result "LINKER_SUPPORTS_${result}")
+
+  # Every subsequent check_cxx_source_compiles((<code> <resultVar>) run will re-use
+  # the cached result rather than performing the check again, even if the <code> changes.
+  # Removing the cached result in order to force the check to be re-evaluated.
+  unset(${result} CACHE)
+
+  if(NOT DEFINED TALF_SOURCE)
+    set(TALF_SOURCE "int main() { return 0; }")
+  endif()
+
+  # This forces running a linker.
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE EXECUTABLE)
+  
+  get_target_property(working_linker_werror_flag internal_werror INTERFACE_LINK_OPTIONS)
+  if(NOT working_linker_werror_flag)
+    set(working_linker_werror_flag)
+  endif()
+  if(CMAKE_VERSION VERSION_LESS 3.14)
+    set(CMAKE_REQUIRED_LIBRARIES ${flag} ${working_linker_werror_flag})
+  else()
+    set(CMAKE_REQUIRED_LINK_OPTIONS ${flag} ${working_linker_werror_flag})
+  endif()
+
+  check_cxx_source_compiles("${TALF_SOURCE}" ${result})
+
+  if(${result})
+    if(DEFINED TALF_IF_CHECK_PASSED)
+      target_link_options(${target} INTERFACE ${TALF_IF_CHECK_PASSED})
+    else()
+      target_link_options(${target} INTERFACE ${flag})
+    endif()
+  elseif(DEFINED TALF_IF_CHECK_FAILED)
+    target_link_options(${target} INTERFACE ${TALF_IF_CHECK_FAILED})
+  endif()
+
+  set(${TALF_RESULT_VAR} "${${result}}" PARENT_SCOPE)
+endfunction()
+
+if(NOT TARGET internal_werror)
+  add_library(internal_werror INTERFACE)
+endif()
+if(MSVC)
+  set(warning_as_error_flag /WX)
+elseif(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+  set(warning_as_error_flag -Wl,-fatal_warnings)
+else()
+  set(warning_as_error_flag -Wl,--fatal-warnings)
+endif()
+try_append_linker_flag(internal_werror "${warning_as_error_flag}")
+unset(warning_as_error_flag)