------------------------------------------------------------------------
FreeBSD 10.3 and 11.1:

tar xf $G/gcc/gcc-5.5.0.gz

cd gcc-5.5.0

cp config/dfp.m4 config/dfp.m4.org
cp libgcc/config.host libgcc/config.host.org

patch -p0 < $G/gcc/gcc-5.5.0.patch.1
patch -p0 < $G/gcc/gcc-5.5.0.patch.2

cd ..

unsetenv CONFIG_SITE
set path= ( /bin /usr/bin /sbin /usr/sbin /usr/local/bin /usr/local/sbin )
echo $path
$B/df -h .
(chdir gcc-5.5.0; $B/diff -c1 config/dfp.m4.org      config/dfp.m4)
(chdir gcc-5.5.0; $B/diff -c1 libgcc/config.host.org libgcc/config.host)

env -i  PATH=$PATH                              \
    HOME=$HOME                                  \
    SHELL=/usr/local/bin/bash                   \
    CC=/usr/local/bin/gcc5                      \
    CXX=/usr/local/bin/g++5                     \
    LANGS=c,c++,fortran,go,lto,objc,obj-c++     \
    MAKEFLAGS=-j32                              \
    $G/gcc/build-dgcc.sh gcc-5.5.0