cmake: Print compiler and linker flags in summary

cmake/module/GetTargetInterface.cmake

@@ -0,0 +1,53 @@
+# 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)
+
+# Evaluates config-specific generator expressions in a list.
+# Recognizable patterns are:
+#  - $<$<CONFIG:[config]>:[value]>
+#  - $<$<NOT:$<CONFIG:[config]>>:[value]>
+function(evaluate_generator_expressions list config)
+  set(input ${${list}})
+  set(result)
+  foreach(token IN LISTS input)
+    if(token MATCHES "\\$<\\$<CONFIG:([^>]+)>:([^>]+)>")
+      if(CMAKE_MATCH_1 STREQUAL config)
+        list(APPEND result ${CMAKE_MATCH_2})
+      endif()
+    elseif(token MATCHES "\\$<\\$<NOT:\\$<CONFIG:([^>]+)>>:([^>]+)>")
+      if(NOT CMAKE_MATCH_1 STREQUAL config)
+        list(APPEND result ${CMAKE_MATCH_2})
+      endif()
+    else()
+      list(APPEND result ${token})
+    endif()
+  endforeach()
+  set(${list} ${result} PARENT_SCOPE)
+endfunction()
+
+
+# Gets target's interface properties recursively.
+function(get_target_interface var config target property)
+  get_target_property(result ${target} INTERFACE_${property})
+  if(result)
+    evaluate_generator_expressions(result "${config}")
+    list(JOIN result " " result)
+  else()
+    set(result)
+  endif()
+
+  get_target_property(dependencies ${target} INTERFACE_LINK_LIBRARIES)
+  if(dependencies)
+    evaluate_generator_expressions(dependencies "${config}")
+    foreach(dependency IN LISTS dependencies)
+      if(TARGET ${dependency})
+        get_target_interface(dep_result "${config}" ${dependency} ${property})
+        string(STRIP "${result} ${dep_result}" result)
+      endif()
+    endforeach()
+  endif()
+
+  set(${var} "${result}" PARENT_SCOPE)
+endfunction()