This is the way MPIR/GMP was ment to work , if you set CFLAGS or most other options then you have to be prepared to set a lot of the other options manually ,
ABI=32 or 64 or whatever is the proper way to set the ABI , the configure mechanism is too complicated already , for it to know all the flags and compiler options
which might change the ABI
I'm thinking of changing the way the default ABI is chosen , because currently the best is chosen which is not what other package choose , they choose the default OS
ABI , leading to mismatches in builds
Jason