arc: libc, libgloss: Remove .file directive from .S files
Assembler for ARCv2 always extends the name provided by
.file directive to an absolute form.
On ARCv3 targets .file directive forces assembler to put
a provided string to DW_AT_name field as is without
extending to an absolute path. Then GDB cannot find
source files because of it.
The best way to fix this issue is just delete lines
with .file directive in .S files and let the compiler
to decide what DW_AT_name must contain. Particularly,
the compiler fills this filed by an absolute path to
a .S file because only absolute paths are used in
toolchain's build process.