This also solves a dependency declaration issue in WorkerSleepExample:
Prior to this change, a clean build could potentially result in

ninja  -C build
ninja: Entering directory `build'
[13/57] Compiling C++ object apps/worker_sleep_example.p/WorkerSleepExample.cpp.o
FAILED: apps/worker_sleep_example.p/WorkerSleepExample.cpp.o
ccache c++ -Iapps/worker_sleep_example.p -Iapps -I../apps -Iemper -I../emper -Iemper/include -I../emper/include -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wnon-virtual-dtor -Wextra -Wpedantic -Werror -std=c++17 -O2 -g -Wno-non-virtual-dtor -MD -MQ apps/worker_sleep_example.p/WorkerSleepExample.cpp.o -MF apps/worker_sleep_example.p/WorkerSleepExample.cpp.o.d -o apps/worker_sleep_example.p/WorkerSleepExample.cpp.o -c ../apps/WorkerSleepExample.cpp
../apps/WorkerSleepExample.cpp:12:10: fatal error: emper-version.h: No such file or directory
   12 | #include "emper-version.h"        // for EMPER_FULL_VERSION
      |          ^~~~~~~~~~~~~~~~~
compilation terminated.
[17/57] Generating emper-version.h with a custom command
ninja: build stopped: subcommand failed.
make: *** [Makefile:23: build] Error 1

because worker_sleep_example_exec should have also depend on
emper_version_h. However this is obviously error prone, as users
easily forget to add this dependency. Instead we add
emper::getFullVersion() which is part of the EMPER shared object (not
just of a single header).