On AIX 4.1, g77 might not build with the native (non-GNU) tools due to a linker bug in coping with the -bbigtoc option which leads to a `Relocation overflow' error. The GNU linker is not recommended on current AIX versions, though; it was developed under a now-unsupported version. This bug is said to be fixed by `update PTF U455193 for APAR IX75823'.
Compiling with -mminimal-toc might solve this problem, e.g. by adding
BOOT_CFLAGS='-mminimal-toc -O2 -g'
make bootstrap command line.