cmake: Add WERROR option

Author: hebasto

CMakeLists.txt

@@ -106,6 +106,7 @@ cmake_dependent_option(BUILD_WALLET_TOOL "Build bitcoin-wallet tool." ${BUILD_TE
 
 option(ENABLE_HARDENING "Attempt to harden the resulting executables." ON)
 option(REDUCE_EXPORTS "Attempt to reduce exported symbols in the resulting executables." OFF)
+option(WERROR "Treat compiler warnings as errors." OFF)
 option(WITH_CCACHE "Attempt to use ccache for compiling." ON)
 
 option(WITH_NATPMP "Enable NAT-PMP." OFF)
@@ -412,6 +413,19 @@ if(REDUCE_EXPORTS)
   try_append_linker_flag("-Wl,-no_exported_symbols" VAR CMAKE_EXE_LINKER_FLAGS)
 endif()
 
+if(WERROR)
+  if(MSVC)
+    set(werror_flag "/WX")
+  else()
+    set(werror_flag "-Werror")
+  endif()
+  try_append_cxx_flags(${werror_flag} TARGET core_interface SKIP_LINK RESULT_VAR compiler_supports_werror)
+  if(NOT compiler_supports_werror)
+    message(FATAL_ERROR "WERROR set but ${werror_flag} is not usable.")
+  endif()
+  unset(werror_flag)
+endif()
+
 find_package(Python3 3.9 COMPONENTS Interpreter)
 if(Python3_EXECUTABLE)
   set(PYTHON_COMMAND ${Python3_EXECUTABLE})
@@ -471,6 +485,7 @@ message("C++ compiler .......................... ${CMAKE_CXX_COMPILER_ID} ${CMAK
 include(FlagsSummary)
 flags_summary()
 message("Attempt to harden executables ......... ${ENABLE_HARDENING}")
+message("Treat compiler warnings as errors ..... ${WERROR}")
 message("Use ccache for compiling .............. ${WITH_CCACHE}")
 message("\n")
 if(configure_warnings)