--prefix= --with-gxx-include-dir (Installing GCC: Configuration)

--prefix=dirnameSpecify the toplevel installation directory. This is the recommended way to install the tools into a directory other than the default. The toplevel installation directory defaults to /usr/local.

We highly recommend against dirname being the same or a subdirectory of objdir or vice versa. If specifying a directory beneath a user's home directory tree, some shells will not expand dirname correctly if it contains the ‘~’ metacharacter; use $HOME instead.

 

--with-gxx-include-dir=dirnameSpecify the installation directory for G++ header files. The default depends on other configuration options, and differs between cross and native configurations.

 

参考：https://gcc.gnu.org/install/configure.html