Ticket #547: minor fix: compilation fails using multi-proc due to concurrent access on same custom command

Ticket #547 (closed): minor compilation fix: compilation fails using multi-proc due to concurrent C addspace generation dependency

When compiling using multi-proc (i.e. using build.sh script with multi-core available), the C demo address space generation dependency can be evaluated whereas the same generation has already begun. Therefore the compilation fails because it uses an incomplete generated version of the C file for a concurrent compilation target.

Define separated C address space files for each test even if the source XML file is the same.