This article is from the Amiga FAQ, by Ignaz Kellerer with numerous contributions by others.
Starting from this release an AmigaDOS compliant library is provided, thanks to libnix authors (Matthias Fleischer and Gunther Nikl).
Anyway if you want to rebuild one, there are two methods:
1) Using hunk2gcc; the AmigaDOS object converter made by Markus Wild. To achieve this, simply grab a copy of latest amiga.lib (from Commodore Development Kit, see Includes) and make a new directory where you want your converted object files to go, cd into it, and enter
hunk2gcc amiga.lib [..further libs if you like..]
This generates an a.out object file for every program unit present in the hunk file (in this case, from amiga.lib).
As the final step convert all those files into an a.out style library by issuing:
ar qc libamiga.a obj.* ranlib libamiga.a
The ranlib run builds a symbol table in the archive, and makes accesses to the library much faster.
2) Creating a libamiga.a library with libnix is fairly easy, but takes some time. Just uncompress sources.lha from libnix distribution and run a `make libamiga.a'.
*Note:* As long as you make no AmigaDOS specific calls, you can create a dummy library using:
cat "int dummy;" >dummy.c gcc -c dummy.c ar crv libamiga.a dummy.o mv libamiga.a gcc:lib