-b 32 -V -1 -A x86x87
-b 32
ensures that you build the 32-bit libraries, which is necessary,
since most older machines do not implement x86-64 (AMD64). The
-V -1
says use no ISA extensions beyond the original x86 spec.
The -A x86x87
selects an artificial architecture
providing you with portable (but slow!) architectural defaults.