juju should compile with gccgo

[Dave Cheney]

The best available path to providing juju on aarch64 machines that do not support a 32bit compat environment is porting gccgo to run on aarch64. To support this, juju itself needs to be buildable via gccgo (currently the only tested compiler is the gc suite)

[John A Meinel (jameinel)]

We may want gccgo in general on Ubuntu because it has a better story about shared libraries and distribution needs.

[Dave Cheney (dave-cheney)]

Marking this as done (Fix Released), within a first approximation juju-core 1.15.0 compiles with gccgo. The remaining issues are around LD_LIBRARY_PATH which would be fixed by distributing gccgo via PPA rather than hand compiling it.

lucky(/tmp) % env LD_LIBRARY_PATH=/opt/gccgo/lib64 ./juju version
1.15.0-raring-amd64
lucky(/tmp) % env LD_LIBRARY_PATH=/opt/gccgo/lib64 ldd ./juju
        linux-vdso.so.1 => (0x00007fff4fb67000)
        libgo.so.4 => /opt/gccgo/lib64/libgo.so.4 (0x00007fc4a73ab000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fc4a7171000)
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fc4a6e6b000)
        libgcc_s.so.1 => /opt/gccgo/lib64/libgcc_s.so.1 (0x00007fc4a6e55000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fc4a6a8d000)
        /lib64/ld-linux-x86-64.so.2 (0x00007fc4a7ee2000)