build: Fix configure with older autotools
build: Fix configure with older autotools

Fixes this:
configure.ac:45: error: AC_PROG_CC cannot be called after AM_PROG_CC_C_O
config/m4/ax_prog_cc_for_build.m4:38: AX_PROG_CC_FOR_BUILD is expanded
from...

Signed-off-by: Ola Jeppsson <793f970c52ded1276b9264c742f19d1888cbaf73@adapteva.com>

mateunho/pal,parallella/pal,aolofsson/pal,parallella/pal,eliteraspberries/pal,eliteraspberries/pal,parallella/pal,debug-de-su-ka/pal,eliteraspberries/pal,aolofsson/pal,mateunho/pal,debug-de-su-ka/pal,aolofsson/pal,mateunho/pal,mateunho/pal,mateunho/pal,parallella/pal,debug-de-su-ka/pal,aolofsson/pal,parallella/pal,eliteraspberries/pal,debug-de-su-ka/pal,eliteraspberries/pal,debug-de-su-ka/pal