[RFA] unload.exp path fix

[Andrew Cagney]

Randolph Chung wrote:
> According to gdb.exp, gdb_get_line_number takes paths relative to
> ${srcdir}/${subdir}, so we should not pass in ${srcdir}/${subdir}.
> 
> without this fix, i am seeing:
> ERROR: couldn't open "../../../gdb-cvs/gdb/testsuite/gdb.base/../../../gdb-cvs/gdb/testsuite/gdb.base/unloadshr.c": no such file or directory

Hmm, yes (but please state what it as tested on)

> -set unloadshr_line [gdb_get_line_number "unloadshr break" ${srcdir}/${subdir}/${libsrcfile}]
> +set unloadshr_line [gdb_get_line_number "unloadshr break" ${libsrcfile}]
>  
>  gdb_test "run" \
>  "Starting program.*unload.*

Andrew