go 1.11 added modules, which are cached locally. The go developers have
decided to make this cache read-only (golang/go#27455), which causes
problems with package clean / autoremove (#7635).

This adds a call to clear this cache right after building, as currently
there is no easy way to hook into autoremove (it may be possible to hook
into package clean).

This also adds whitespace (blank lines) to certain places in make
output, to aid debugging.

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

Go 1.11 added softfloat support for 64-bit MIPS systems[1], so this also
adds builds for mips64 and mips64el.

[1] https://golang.org/doc/go1.11#mips

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

This updates GoPackage/Build/Compile in golang-package.mk to accept
additional arguments that are passed to the go command line.

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>