$ wget https://ftp.jaist.ac.jp/pub/GNU/gcc/gcc-10.2.0/gcc-10.2.0.tar.xz
$ tar xvf gcc-10.2.0.tar.xz
$ cd gcc-10.2.0/
$ unset LIBRARY_PATH CPATH C_INCLUDE_PATH PKG_CONFIG_PATH CPLUS_INCLUDE_PATH INCLUDE
$ mkdir build
$ cd build
$ ../configure --prefix=/opt/gcc/10.2.0 --enable-languages=c,c++,fortran --disable-multilib --disable-bootstrap
$ make -j
$ make install