Run tests with dwo symbol file
dwo symbol files are generated when code compiled with the "-gsplit-dwarf" command option (https://gcc.gnu.org/wiki/DebugFission). This CL modifies the test system to run tests with inferiors compile with the "-gsplit-dwarf"
I tested "-gsplit-dwarf" on OSX, Linux and Android and there are no regression on these platform, for other platforms I have no access to at the moment but all recent compiler should support split dwarf (gcc 4.7+, clang 3.5+). If somebody know about configurations where split dwarf test should be disabled then please let me know, or disable them after commit by setting dont_do_dwo_test in dotest.py (see setting of dont_do_dsym_test in line 1520)