Make running tests portable (switch to relative paths, isolation environment)

[ladisgin]

In the current solution we can't run tests if we pass them to another pc

Now

• Use absolute path to source in MakeFile
• Write intermediate files into tmp directory.

Solution

• Move MakeFile for run tests into tests folder
• Replace tmp directory by directory inside ${project}/${build}/utbot_build
• Change to relative paths in MakeFile

[antipeon]

Design

• We work with absolute paths but when it comes to writing paths to file (e.g MakefilePrinter, TestPrinter) we convert them to relative: absolute_path/smt -> $path/smt

• For some $path variables we can write definition such that there is no need to change it on another machine. For example, we know $PROJECT_DIR variable since we know the relative path of current makefile to project directory.

• Other $path variables we write mostly as follows:

ifndef $path
  $path = default/path
endif

For now $UTBOT_ALL$, $linker, $PRIVATE_LIB are examples of such $path variables

• For the last type of variables we give priority to our paths. If the machine where tests are run doesn't have such variables we allow their definition. Examples of such variables are: $compiler, $compiler++, $GTEST.

• Careful to convert absolute paths not only in makefiles, but stubs, srcs, etc.