Jetson TX1 rebuild Kernel, error and solution

Thanks everyone for great instructions and links, I was able to download/install cross compilers and implement 2 workarounds: 

#(1). To Fix 'error: r7 cannot be used in asm here' problem
# add he followin
# KBUILD_CFLAGS_KERNEL := -fomit-frame-pointer
# to line 378 of makefile
#(2). To fix error "logical not is only applied to the left hand side of comparison"
# Chnage line 1065 of "tegra21_clocks.c" to:
# c->state = ((!is_lp_cluster()) == (c->u.cpu.mode == MODE_G)) ? ON : OFF;
#