monero, monero-gui: fix build against current protobuf

[vxfemboy]

Both packages fail to build against current protobuf (35.1) with:

error: no matching function for call to 'hw::trezor::MessageMapper::get_message_wire_number(absl::string_view)'

Root cause

cmake/CheckTrezor.cmake gates monero's own absl::string_view overload of get_message_wire_number() — which exists precisely to handle protobuf's Descriptor::name() now returning absl::string_view — behind Protobuf_VERSION VERSION_GREATER_EQUAL 22.0.

Protobuf_VERSION, as CMake's bundled FindProtobuf.cmake parses it from protoc --version, now reports a decoupled generator-version axis (libprotoc 7.35.1) distinct from the library release version (35.1). So Protobuf_VERSION becomes 7.35.1, and 7 < 22 silently fails the check — even though this protobuf's Descriptor::name() unconditionally returns absl::string_view.

Fix

Replace the version-number comparison with a check_cxx_source_compiles probe of the actual API surface, so detection stays correct regardless of how protobuf numbers future releases.

monero-gui vendors its own internal copy of the monero core (post_extract()), including the same cmake/CheckTrezor.cmake — same root cause, same fix, applied to the vendored path.

Verification

• Traced the exact root cause: extracted the failing build's CMakeCache.txt, confirmed Protobuf_VERSION resolved to 7.35.1 (FIND_PACKAGE_MESSAGE_DETAILS_Protobuf:INTERNAL=[...][v7.35.1()]), confirmed via check_cxx_source_compiles in /usr/share/cmake-4.2/Modules/FindProtobuf.cmake that this is exactly how the module derives the version.
• Live-tested the patch inside the xbps-src chroot before writing the final patch file: all 3 previously-failing objects (messages_map.cpp.o, device_trezor_base.cpp.o, device_trezor.cpp.o) compile clean.
• Full clean ./xbps-src pkg monero and ./xbps-src pkg monero-gui builds succeed end-to-end.
• Installed both on a real host alongside the libprotobuf upgrade (35.1) that was previously blocked — xbps refused to touch libprotobuf while the installed monero/monero-gui still required libprotobuf.so.25.2.0. Confirmed both binaries now link against libprotobuf.so.35.1.0 and run correctly (monerod --version, monero-wallet-gui linkage).

Test plan

• monero: full clean build succeeds
• monero-gui: full clean build succeeds
• Both install cleanly alongside libprotobuf-35.1_1 on a real system
• ldd confirms both link against libprotobuf.so.35.1.0
• monerod --version runs correctly