Not able to complete rocket tool installation due to ar utility

Hello Friends,

I am trying to install rocket-tool and using below commands to install it.:
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$ git clone https://github.com/freechipsproject/rocket-tools
$ cd rocket-tools
$ git submodule update --init --recursive
$ export RISCV=/path/to/install/riscv/toolchain
$ export MAKEFLAGS="$MAKEFLAGS -jN" # Assuming you have N cores on your host system
$ ./build.sh
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**While performing "build.sh", it gives below "ar" related error in riscv-isa-sim build process.**

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ar rcs -o elfloader.o htif.o memif.o dtm.o syscall.o device.o rfb.o context.o htif_pthread.o htif_hexwriter.o dummy.o option_parser.o term.o tsi.o
ar: illegal option combination for -r
usage: ar -d [-TLsv] archive file ...
ar -m [-TLsv] archive file ...
ar -m [-abiTLsv] position archive file ...
ar -p [-TLsv] archive [file ...]
ar -q [-cTLsv] archive file ...
ar -r [-cuTLsv] archive file ...
ar -r [-abciuTLsv] position archive file ...
ar -t [-TLsv] archive [file ...]
ar -x [-ouTLsv] archive [file ...]
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I tried to modify Makefile and removed -o option but still seems command requires *.a file.
To me it seems a Bug in code. Please suggest the working code for ar command.

I am using Mac OS sierra 10.12.06.

Start with build.sh and the Makefile involved in the riscv-isa-sim build, then reproduce the ar command on macOS Sierra. Check how the archive command is generated and verify the build completes with a valid archive after the platform-specific issue is addressed.

Written by the indexing model from the issue text.