Fix unexpected argument splitting

This doesn't work:

    $ isolate-gpu -d 2 ./gdb -nx -q --data-directory=data-directory testsuite/outputs/gdb.rocm/simple/simple -ex "with breakpoint pending on -- break do_an_addition"
    Excess command line arguments ignored. (pending ...)
    Reading symbols from testsuite/outputs/gdb.rocm/simple/simple...
    /home/smarchi/build/binutils-gdb-amd-staging/gdb/breakpoint: No such file or directory.
    Missing arguments.
    (gdb)

The argument `"with breakpoint ..."` gets split along the way.  Fix it
by using "$@", which doesn't split the args that contain spaces.

Change the "else" portion just to match the style of the "if" section.

With this patch, I get the expected:

    $ isolate-gpu -d 2 ./gdb -nx -q --data-directory=data-directory testsuite/outputs/gdb.rocm/simple/simple -ex "with breakpoint pending on -- break do_an_addition"
    Reading symbols from testsuite/outputs/gdb.rocm/simple/simple...
    Function "do_an_addition" not defined.
    Breakpoint 1 (do_an_addition) pending.
    (gdb)

Author: simark

entrypoint.sh

@@ -2,12 +2,11 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 # Author  : Pedro Alves (pedro@palves.net)
 
+cd "$ISOLATE_GPU_CWD" || exit 1
+unset ISOLATE_GPU_CWD
+
 if [ $# -gt 0 ]; then
-    exec sh -c "cd $ISOLATE_GPU_CWD && \
-		unset ISOLATE_GPU_CWD && \
-		$*"
+    exec "$@"
 else
-    exec sh -c "cd $ISOLATE_GPU_CWD && \
-		unset ISOLATE_GPU_CWD && \
-		$SHELL --login"
+    exec $SHELL --login
 fi