golang: Reorganize GoPackage/Environment and Makefile variables

* Move more environment variables into GoPackage/Environment
* Split GoPackage/Environment into target and build sections
* Do not set GOROOT_FINAL for Go packages (setting it should only affect
  the Go compiler and not Go packages)
* Set CGO_LDFLAGS to $(TARGET_LDFLAGS)
* Move GO_TARGET_* variables from golang-values.mk, and GO_VERSION_*
  variables from golang-version.mk, into golang/Makefile

This also updates runc, containerd, and docker-ce to reflect the changes
in GoPackage/Environment.

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

utils/docker-ce/Makefile

@@ -2,7 +2,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=docker-ce
 PKG_VERSION:=19.03.5
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 PKG_LICENSE:=Apache-2.0
 PKG_LICENSE_FILES:=components/cli/LICENSE components/engine/LICENSE
 
@@ -78,13 +78,7 @@ endif
 
 define Build/Compile
 	( \
-		export GOPATH=$(GO_PKG_BUILD_DIR) \
-			GOCACHE=$(GO_PKG_CACHE_DIR) \
-			GOTMPDIR=$(GO_PKG_TMP_DIR) \
-			GOROOT_FINAL=$(GO_TARGET_ROOT) \
-			CC=$(TARGET_CC) \
-			CXX=$(TARGET_CXX) \
-			$(call GoPackage/Environment) \
+		export $(call GoPackage/Environment) \
 			GITCOMMIT=$(PKG_SOURCE_VERSION) \
 			DOCKER_GITCOMMIT=$(PKG_SOURCE_VERSION) \
 			DOCKER_BUILDTAGS='$(BUILDTAGS)' \