Use more appropriate cross-compiler installation locations
The toolchain.sh and configure.sh scripts use the
$XDG_DATA_HOME/HelenOS/cross (i.e. $HOME/.local/share/HelenOS/cross)
location by default now. This allows the cross-compiler to be
installed without super user privileges and thus hopefully lowers the
entry barrier for newcomers.
To install the cross-compiler to a system-wide location, run the
toolchain.sh script with the —system-wide option. The default
system-wide location is /opt/HelenOS/cross now.
The configure.sh script falls back to /opt/HelenOS/cross and the
previously used /usr/local/cross. Thus recompiling an already
installed cross-compiler toolchain is not necessary.
The possibility to override the cross-compiler location using
$CROSS_PREFIX or having the cross-compiler available in $PATH
retained.
