When ld version is too old (Debian 7 comes with version 2.2 which is too
old), golang testsuite fail with:

binutils_test.go:237: SourceLine for main: expect [{main /tmp/hello.c 3}]; got [{main  0}]

see also https://github.com/golang/go/issues/26584

We explicitly use gcc 8.2, but what we need is gcc > 5.5 because of
https://github.com/golang/go/issues/24046
When 8.2 (or newer) becomes the default SlapOS gcc, there should be no
problem in dropping the explicit version and using ${gcc:location} here.