tcf-agent: Add $@ to RANLIB

tcf-agent: Add $@ to RANLIB

tcf-agent calls RANLIB ( if defined ) after calling AR to
create the archive [1], when RANLIB is set to gcc-ranlib this goes
unnoticed, since calling gcc-ranlib without any arguments silenlty
does nothing and exits with return code 0, however, calling binutils
ranlib or llvm-ranlib does demand library name as commandline option
and since it is not there it exits with code 1

aarch64-poky-linux-musl-llvm-ranlib
OVERVIEW: LLVM ranlib

Generate an index for archives

USAGE: aarch64-poky-linux-musl-llvm-ranlib archive...

OPTIONS:
   -h --help             - Display available options
   -V --version          - Display the version of this program
   -D                    - Use zero for timestamps and uids/gids (default)
   -U                    - Use actual timestamps and uids/gids
   -X{32|64|32_64|any}   - Specify which archive symbol tables should be
generated if they do not already exist (AIX OS only)
aarch64-poky-linux-musl-llvm-ranlib: error: an archive name must be
specified
make: *** [Makefile:53: obj/GNU/Linux/a64/Debug/libtcf.a] Error 1

When we add $@, to RANLIB then it becomes the make variable,
$@ - An automatic Makefile variable that expands to the target name (the
file being built)

so the makefile target now rightly adds the .a filename to RANLIB call.

Sent a patch upstream to add RANLIB for linux [2]

[1] https://gitlab.eclipse.org/eclipse/tcf/tcf.agent/-/blob/master/agent/Makefile?ref_type=heads#L53
[2] https://gitlab.eclipse.org/eclipse/tcf/tcf.agent/-/merge_requests/7

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>