golang: Add support for ASLR/PIE for Go packages

This adds support to compile position-independent executables for
packages that use golang-package.mk.

Go packages will have PIE enabled if:
* Go supports PIE on the target platform;
* CONFIG_PKG_ASLR_PIE is selected; and
* PKG_ASLR_PIE (for the package) is not set to 0

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>