netns: change build target to 'build' instead of 'static'

Attempting to build for x86-64 will result in an error:
   cannot find package runtime/cgo (using -importcfg)
   ...go/pkg/tool/linux_amd64/link: cannot open file : open : no such file or directory

As a workaround we switch the build target to 'build' which results in
a slightly smaller executable but does mean that several dynamic
libraries are required to run the generated executable. This shouldn't
be a problem as the build system will ensure the libraries are present
on images where the executable will be included. This change only
means the executable can't be copied as a single entity to a different
machine and run.

We do also patch the Makefile to allow the 'static' target to build
successfully and in the patch commit log we describe the issue in full
(at least in as much detail as we currently have on the issue). But
since the issue isn't fully understood we don't recommend the 'static'
build to be used at this time, thus default to the 'build' target.

Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

recipes-networking/netns/files/Makefile-force-rebuilding-all-packages-to-avoid-cgo.patch

@@ -0,0 +1,54 @@
+From 09524d187ef108784c854a0c247ac6476a10bb67 Mon Sep 17 00:00:00 2001
+From: Mark Asselstine <mark.asselstine@windriver.com>
+Date: Mon, 18 Mar 2019 14:04:16 -0400
+Subject: [PATCH] Makefile: force rebuilding all packages to avoid cgo
+
+We are running into an issue when attempting to build 'static',
+similar to what is described by
+
+https://plus.google.com/117192131596509381660/posts/eNnNePihYnK
+and
+https://github.com/golang/go/issues/9369
+
+In our case we can see that it manifests as a build error
+
+    cannot find package runtime/cgo (using -importcfg)
+    ...go/pkg/tool/linux_amd64/link: cannot open file : open : no such file or directory
+
+Although the descriptions of issue indicate that newer versions of GO,
+such as the version we are using, should not have this issue it is
+clear from the error that cgo is being referenced when it should be
+out of the picture.
+
+Interesting enough this issue only manifests when we are building on
+x86-64 and building for x86-64 which might indicate that GO might be
+finding -native packages and not -cross packages.
+
+This change works around the issue and will allow for the building of
+the 'static' make target, but at this time and until the issue is
+completely understood, it is recommended that the 'build' target is
+used.
+
+Upstream-Status: Inappropriate [only an issue with our builds]
+
+Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
+---
+ Makefile | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/Makefile b/Makefile
+index 476cb9b..ecd0df4 100644
+--- a/src/import/Makefile
++++ b/src/import/Makefile
+@@ -41,7 +41,7 @@ $(NAME): *.go VERSION.txt
+ .PHONY: static
+ static: ## Builds a static executable
+ 	@echo "+ $@"
+-	CGO_ENABLED=0 $(GO) build \
++	CGO_ENABLED=0 $(GO) build -a -pkgdir dontusecurrentpkgs \
+ 				-tags "$(BUILDTAGS) static_build" \
+ 				${GO_LDFLAGS_STATIC} -o $(NAME) .
+ 
+-- 
+2.7.4
+

recipes-networking/netns/netns_git.bb

@@ -5,6 +5,7 @@ LIC_FILES_CHKSUM = "file://src/import/LICENSE;md5=48ef0979a2bcc3fae14ff30b8a7f5d
 
 SRC_URI = "git://github.com/genuinetools/netns;branch=master \
            file://0001-Allow-selection-of-go-compiler.patch \
+           file://Makefile-force-rebuilding-all-packages-to-avoid-cgo.patch \
           "
 SRCREV = "0da6ab0997707024debe68c91e940c9168041bf8"
 PV = "0.4.0"
@@ -42,7 +43,9 @@ do_compile() {
 	export CGO_LDFLAGS="${BUILDSDK_LDFLAGS} --sysroot=${STAGING_DIR_TARGET}"
 
 	cd ${S}/src/import
-	oe_runmake static
+	# Static builds work but are not recommended. See Makefile*cgo patch.
+	#oe_runmake static
+	oe_runmake build
 }
 
 do_install() {