This adds support to compile host and target Go as position-independent
executables.

Host Go will have PIE enabled if Go supports PIE on the host platform.

Target Go will have PIE enabled if Go supports PIE on the target
platform and CONFIG_PKG_ASLR_PIE is selected.

Go 1.13 supports PIE for x86 and arm targets; mips support is in
progress[1].

[1]: https://github.com/golang/go/issues/21222#issuecomment-542064462

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

From golang.org:
The Go programming language is an open source project to make
programmers more productive.

This commit consists of two "parts":

* golang/host: Main Go compiler for host (installed to
  STAGING_DIR_HOST/lib/go-cross), used to cross-compile Go programs to
  be packaged.

* golang (and golang-src/golang-doc): Main Go compiler for on-target
  development. These packages are quite large, but I would expect only
  developers to install these.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>