/bin/sh: sparc64-linux-gcc: not found
This would be a cross-compiler for Sparc64 target. Sparc64 emulation is not usable for anything yet, please try configuring for Sparc32 instead. That in turn needs sparc-linux-gcc, a cross compiler for Sparc32. If you have access to a Sparc machine (real or Qemu one), you can compile there with a regular gcc.