Making the src-gen folder more stand-alone

[edwardalee]

The src-gen folder currently generated by lfc does not quite contain enough information to build the generated C code. To reproduce:

cd test/C
lfc src/Minimal.lf
cd src-gen/Minimal
rm -rf build
mkdir build
cd build
cmake ../
make

This fails with

/Users/eal/lingua-franca-intellij/test/C/src-gen/Minimal/core/../include/core/platform.h:50:2: error: Must define either LF_UNTHREADED or LF_THREADED runtime
#error Must define either LF_UNTHREADED or LF_THREADED runtime
 ^
1 error generated.

In order to get the program to build, you have issue the following incantation:

cmake -DLF_REACTION_GRAPH_BREADTH=1 -DLF_THREADED=1 -DNUMBER_OF_WORKERS=0 -DSCHEDULER=NP -DLOG_LEVEL=2 -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/Users/eal/lingua-franca-intellij/test/C -DCMAKE_INSTALL_BINDIR=bin ../

@erlingrj suggested that a simple solution would be to write the default/provided target properties to both CMakeLists.txt and CompileDefinitions.txt. We can put the variables behind statements like this:

if (NOT DEFINED NUMBER_OF_WORKERS)
  set(NUMBER_OF_WORKERS 42 )
endif()

This way we get (1) plug-and-play integration with cmake, (2) easy to extend to other build system because the info is also readily available in CompileDefinitions.txt and (3) change target properties without rebuilding by changing passing arguments to cmake.

[erlingrj]

Now that the compiler generates vscodes files I would say that this is less of an issue. But still would be a nice feature. In fact, it might make the generation of vscode files redundant.