/usr/bin/ld: cannot find -lgcc
/usr/bin/ld: cannot find -lgcc_s
/usr/bin/ld: cannot find crtn.o: No such file or directory
collect2: error: ld returned 1 exit status
configure: error: I suspect your system does not have 32-bit developement libraries (libc and headers). If you have them, rerun configure with --enable-multilib. If you do not have them, and want to build a 64-bit-only compiler, rerun configure with --disable-multilib.
意思是，我電腦默認的編譯配置是32位和64位，但是32位的dev lib不齊全，建議最好關掉32位，進行如下操作：
~/gcc-build/gcc-3.6.0/configure --disable-multilib --enable-languages=c,c++
之後就OK了，所有的cannot find和error都沒了！
安裝方法：https://askubuntu.com/questions/864893/update-gcc-to-the-6-3-version
wget https://ftp.gnu.org/gnu/gcc/gcc-6.3.0/gcc-6.3.0.tar.bz2
tar jxvf gcc-6.3.0.tar.bz2
cd gcc-6.3.0
./contrib/download_prerequisites
cd ~
mkdir gcc-build && cd gcc-build
../gcc-6.3.0/configure -v --prefix=$HOME/gcc-6.3.0
make
sudo make install