gdbserver-base.exp: Copy file to standard output directory in ${board}_download

gdbserver-base.exp is used as the base for both native-gdbserver.exp and
native-extended-gdbserver.exp.  (Despite its name, it should really be
considered as a "local-gdbserver-base", as it's not really appropriate to
implement a remote gdbserver board.)

Currently, the _download procedure is implemented as a no-op (it returns
the source file path).  Because of the SONAME change, The fast
tracepoint tests now require the executable and the IPA
(libinproctrace.so) to be located in the same directory (see [1]).  When
using the native-gdbserver board, because _download returns the original
file path, the executable does not end up in the same directory as the
library, and it fails to execute.

In more general terms, with the recent changes, the testsuite now
assumes that when it does

  ${board}_download <source path 1> <destination path 1>
  ${board}_download <source path 2> <destination path 2>

where the destination paths are relative (generally just the file name),
both files will end up in the same base directory.  That assumption does
not hold for the current implementation in gdbserver-base.exp.

The proper fix would be to make native-gdbserver non-remote, so that
gdb_remote_download would not call DejaGnu's remote_download (see [2]).
We could then get rid of ${board}_download in gdbserver-base.exp.
However, that will likely take some time to complete.  In the mean time,
in order to make the fast tracepoint tests pass, we can simply copy the
file to the standard output directory.  Basically, it just mimics what
gdb_remote_download would do if the board wasn't flagged as remote.

Note that I missed these failures originally because I had a
libinproctrace.so in /usr/local/lib.  So, even though libinproctrace.so
wasn't copied to the test output directory, it did find the one in
/usr/local/lib.  It would be nice to find a way to protect against this,
as it could easily happen again...

Regtested with unix, native-gdbserver and native-extended-gdbserver, and
didn't see anything notable, except the ftrace tests now passing for
native-gdbserver.

[1] https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=6e774b13c3b81ac2599812adf058796948ce7e95
[2] https://sourceware.org/ml/gdb-patches/2016-04/msg00112.html

gdb/testsuite/ChangeLog:

	* boards/gdbserver-base.exp (${board}_download): Copy source file to
	standard output directory.

1 files changed, 8 insertions, 1 deletions

diff --git a/gdb/testsuite/boards/gdbserver-base.exp b/gdb/testsuite/boards/gdbserver-base.exp
index b6862042b2..02a9244c57 100644
--- a/gdb/testsuite/boards/gdbserver-base.exp
+++ b/gdb/testsuite/boards/gdbserver-base.exp
@@ -41,7 +41,14 @@ proc ${board}_file { dest op args } {
 }
 
 proc ${board}_download { board host dest } {
-    return $host
+    # We pass DEST in standard_output_file, regardless of whether it is absolute
+    # or relative, because we don't want the tests to be able to write outside
+    # their standard output directory.
+    set dest [standard_output_file $dest]
+
+    file copy -force $host $dest
+
+    return $dest
 }
 
 proc ${board}_upload {dest srcfile args} {