How to merge two “ar” static libraries into one?

gistfile1.txt

######################################################################################################
# You can extract the object from both the .a files and create your .a file using the extracted .os: #
######################################################################################################

# Make a .tmp directory where we will extract our .o file later we delete this dir
mkdir .tmp
cd .tmp
ar -x ../libBMDGfx.a
ar -x ../Graphics/3rdParty/FontSupport/harfbuzz-master/build/libharfbuzz.a
ar -rc ../libGfx.a  *.o
#ar -ds ../libGfx.a  *.o
cd ..
rm -rf .tmp