To create a static library use the ar (Archive) command. For example to create the library libMyLib.a from files a.o, b.o, c.o:-
ar -r libMyLib.a a.o b.o c.o
the -r option tells the archiver to insert with replacement, creating the library if necessary.
To type the current contents:-
ar -t libMyLib.a
and to replace e.g. c.o:-
ar -r libMyLib.a b.o