Set DW_AT_comp_dir for each compile unit in dwarf

The dex file don't contain the full path of the compilation dir so we
set it to a symbolic value ($JAVA_SRC_ROOT) what can be remapped by
the tools reading the dwarf information.

Change-Id: Ia011de14a6b36a29b54b3f3fa290cc3157a0b91d
1 file changed