Revert "sphinx: add --with-sphinx-build"

gcc/Makefile.in

gcc/ada/gcc-interface/Make-lang.in

gcc/configure

gcc/configure.ac

gcc/d/Make-lang.in

gcc/fortran/Make-lang.in

gcc/go/Make-lang.in

gcc/jit/Make-lang.in

libgomp/Makefile.in

libgomp/configure

libgomp/configure.ac

libiberty/Makefile.in

libiberty/configure

libiberty/configure.ac

libitm/Makefile.in

libitm/configure

libitm/configure.ac

libquadmath/Makefile.in

libquadmath/configure

libquadmath/configure.ac