snap: use new GOPATH to build image

Use a new GOPATH to build image in order to avoid clashes with user's GOPATH,
otherwise user's kata agent will be used causing problem if that repository is
not up to date.

Signed-off-by: Julio Montes <julio.montes@intel.com>

snap/snapcraft.yaml

@@ -123,6 +123,9 @@ parts:
       - docker.io
       - cpio
     override-build: |
+      # set GOPATH
+      export GOPATH=$(realpath go)
+      mkdir -p "${GOPATH}"
       # go was built in parts/go/build
       export GOROOT=$(realpath ../../go/build)
       export PATH="${GOROOT}/bin:${PATH}"
@@ -138,7 +141,7 @@ parts:
       # use the same go version for all packages
       sed -i 's|^GO_VERSION=.*|GO_VERSION='$(go version | cut -d' ' -f3 | tr -d go)'|g' rootfs-builder/versions.txt
 
-      sudo -E PATH=$PATH make DISTRO=alpine AGENT_INIT=yes USE_DOCKER=1 initrd
+      sudo -E PATH=$PATH make AGENT_VERSION=${SNAPCRAFT_PROJECT_VERSION} DISTRO=alpine AGENT_INIT=yes USE_DOCKER=1 initrd
 
       kata_image_dir=${SNAPCRAFT_PART_INSTALL}/usr/share/kata-containers
       mkdir -p ${kata_image_dir}