[testsuite] Remove BASEDIR

[testsuite] Remove BASEDIR

BASEDIR was added by https://sourceware.org/ml/gdb-patches/2013-10/msg00587.html
in order to handle the different directory layout in serial testing
and parallel testing.  BASEDIR is "gdb.base" in serial testing and is
"outputs/gdb.base/TESTNAME" in parallel testing.  However, it doesn't
work if the GDBserver is in remote target, like this,

$ make check RUNTESTFLAGS='--target_board=remote-gdbserver-on-localhost foll-vfork.exp foll-exec.exp'
FAIL: gdb.base/foll-exec.exp: continue to first exec catchpoint (the program exited)
FAIL: gdb.base/foll-vfork.exp: exec: vfork and exec child follow, to main bp: continue to bp (the program exited)
FAIL: gdb.base/foll-vfork.exp: exec: vfork child follow, finish after tcatch vfork: finish (the program exited)
FAIL: gdb.base/foll-vfork.exp: exec: vfork relations in info inferiors: continue to bp (the program exited)

these tests fail because the executable can't be found.  With target
board native-gdbserver, the program is spawned this way,

 spawn ../gdbserver/gdbserver --once :2347 /scratch/yao/gdb/build-git/x86_64/gdb/testsuite/gdb.base/foll-vfork

so BASEDIR is correct.  However, with target board
remote-gdbserver-on-localhost, the program is spawned

  spawn /usr/bin/ssh -l yao localhost /scratch/yao/gdb/build-git/x86_64/gdb/testsuite/../gdbserver/gdbserver --once :2346 /scratch/yao/gdb/build-git/x86_64/gdb/testsuite/gdb.base/foll-vfork

so BASEDIR (either "gdb.base" or "outputs/gdb.base/TESTNAME") makes no
sense.

I had a fix that pass absolute directory to BASEDIR, but it assumes
that directory structure is the same on build and target, and it
doesn't work in remote host case.  The current fix in this patch is
to get the directory from argv[0].  In any case, the program to be
exec'ed is at the same directory with the main program.

Note that these tests do "next N" to let program stop at the desired
line, but it is fragile, because GDB for different targets may skip
function prologue slightly differently, so I replace some of them by
"tbreak on LINE NUMBER and continue".

gdb/testsuite:

2016-02-04  Yao Qi  <yao.qi@linaro.org>

	* gdb.base/foll-exec-mode.c: Include limits.h.
	(main): Add parameters argc and argv.  Get directory from
	argv[0].
	* gdb.base/foll-exec-mode.exp: Don't pass -DBASEDIR in
	compilation.
	* gdb.base/foll-exec.c: Include limits.h.
	(main): Add parameters argc and argv.
	Get directory from argv[0].
	* gdb.base/foll-exec.exp: Don't pass -DBASEDIR in compilation.
	Adjust tests on the number of lines as source code changed.
	* gdb.base/foll-vfork-exit.c: Include limits.h.
	(main): Add one line of statement before vfork.
	* gdb.base/foll-vfork.c: Include limits.h and string.h.
	(main): Add parameters argc and argv.  Get directory from
	argv[0].
	* gdb.base/foll-vfork.exp: Don't pass -DBASEDIR in compilation.
	(setup_gdb): Set tbreak to skip some source lines.
	* gdb.multi/bkpt-multi-exec.c: Include limits.h.
	(main): Add parameters argc and argv.  Get directory from
	argv[0].
	* gdb.multi/bkpt-multi-exec.exp: Don't pass -DBASEDIR in
	compilation.
	* gdb.multi/multi-arch-exec.c: Include limits.h and string.h.
	(main): Add parameters argc and argv.  Get directory from
	argv[0].
	* gdb.multi/multi-arch-exec.exp: Don't pass -DBASEDIR in
	compilation.