build: Re-enable external signer support for Windows

CMakeLists.txt

@@ -142,7 +142,7 @@ if(WITH_USDT)
   find_package(USDT MODULE REQUIRED)
 endif()
 
-cmake_dependent_option(ENABLE_EXTERNAL_SIGNER "Enable external signer support." ON "NOT WIN32" OFF)
+option(ENABLE_EXTERNAL_SIGNER "Enable external signer support." ON)
 
 cmake_dependent_option(WITH_QRENCODE "Enable QR code support." ON "BUILD_GUI" OFF)
 if(WITH_QRENCODE)