Broken seperate C/C++ compilation with Cabal-2.2 example

This tag provides an example of the "half implementation" of the cxx-options and cxx-sources buildinfo fields for separate compilation of C++ source files (Cabal issue #3700).

There are 7 build targets included in this package:

Type	Name	Status
library	tcm-memo	PASS
executable	exe-no-lib	FAIL
executable	exe-with-lib	PASS
test-suite	test-no-lib	FAIL
test-suite	test-with-lib	PASS
benchmark	bench-no-lib	FAIL
benchmark	bench-with-lib	PASS

The library builds successful. The executable, test-suite, benchmark that depends on the library successfully build. The executable, test-suite, benchmark that do not link depend on the library and instead directly builds the C & C++ sources, fails with undefined references during linking phase. This is because the C++ sources from the cxx-sources are not added to the linking command in the non-library build targets.