chroot: force use specific GCC version

divert_path() { echo $1.real; } ### customizable

divert() { dpkg-divert --divert $(divert_path $1) --rename $1; }

GNUHOST=$(dpkg-architecture -qDEB_HOST_GNU_TYPE)

VERSIONS=(4.6 4.7 4.8 4.9 5)
USE_VERSION=5

BINPATH=/usr/bin
BIN=(g++ gcc gcc-ar gcc-nm gcc-ranlib gcov gcov-tool)
BIN_HACK=(g++ gcc)

for b in ${BIN[@]}; do
    TARGETS=()

    TARGETS=(${TARGETS[@]} ${b})
    for v in ${VERSIONS[@]}; do
        TARGETS=(${TARGETS[@]} ${b}-${v})
    done; unset v

    TARGETS=(${TARGETS[@]} ${GNUHOST}-${b})
    for v in ${VERSIONS[@]}; do
        TARGETS=(${TARGETS[@]} ${GNUHOST}-${b}-${v})
    done; unset v

    for t in ${TARGETS[@]}; do
        divert ${BINPATH}/${t}
        test "$t" = "$b" && continue
        ln -s ${b} ${BINPATH}/${t}
    done; unset t
done; unset b

for b in ${BIN[@]}; do
    cat > ${BINPATH}/${b} <<EOF
#!/bin/sh
exec $(divert_path ${b}-${USE_VERSION}) "\$@"
EOF
    chmod 755 ${BINPATH}/${b}
done; unset b

for bh in ${BIN_HACK[@]}; do
    cat > ${BINPATH}/${bh} <<EOF
#!/bin/sh
exec $(divert_path ${bh}-${USE_VERSION}) "\$@" -march=native -mtune=native -Ofast
EOF
    chmod 755 ${BINPATH}/${bh}
done; unset bh