[rpcsx-os/orbis-kernel] random bugfixes

ipmi: fixed respond sync, get message, try get message, try send message
event: detach event emitter from file
signals: basic implementation
linker: fixed zero symbol relocation, fixed exec relocation
shared_cv/mutex: implement eintr response support
shared_cv: fixed possible loop instead of wait
ipmi: implement invoke async, respond async, get result, get client app id, client get name
rpcsx-os: add safemode flag

rpcsx-os/iodev/devctl.cpp

@@ -17,6 +17,7 @@ static const orbis::FileOps fileOps = {
 };
 
 struct DevCtlDevice : IoDevice {
+  orbis::kstring data;
   orbis::ErrorCode open(orbis::Ref<orbis::File> *file, const char *path,
                         std::uint32_t flags, std::uint32_t mode,
                         orbis::Thread *thread) override {