snap: Migrate from deprecated keywords to "override-build"

Also add verbosity and echo messages to aid debugging.

See #4908

snapcraft.yaml

@@ -24,23 +24,31 @@ parts:
     stage-packages:
       - git
       - python-pygments
-    prepare: |
+    override-build: |
+      echo "\nStarting override-build:"
       export GOPATH=$(dirname $SNAPCRAFT_PART_INSTALL)/go
       export PATH=$GOPATH/bin:$PATH
       cd $GOPATH/src/github.com/gohugoio/hugo
-      go get github.com/magefile/mage
-      mage -v vendor test
-    build: |
-      export GOPATH=$(dirname $SNAPCRAFT_PART_INSTALL)/go
-      export PATH=$GOPATH/bin:$PATH
-      [ "$SNAPCRAFT_PROJECT_GRADE" = "stable" ] && mage hugoNoGitInfo || mage hugo
+      echo ' * Running "go get -v github.com/magefile/mage"...'
+      go get -v github.com/magefile/mage
+      echo ' * Running "mage -v vendor"...'
+      mage -v vendor
+      echo ' * Running "mage -v test"...'
+      mage -v test
+      echo " * Building hugo (build tag: none)..."
+      [ "$SNAPCRAFT_PROJECT_GRADE" = "stable" ] && mage -v hugoNoGitInfo || mage -v hugo
       ./hugo version
+      ldd hugo || :
+      echo " * Building shell completion..."
       ./hugo gen autocomplete --completionfile=hugo-completion
-    install: |
+      echo " * Installing to ${SNAPCRAFT_PART_INSTALL}..."
       install -d $SNAPCRAFT_PART_INSTALL/bin
-      cp -a hugo $SNAPCRAFT_PART_INSTALL/bin/hugo
+      cp -av hugo $SNAPCRAFT_PART_INSTALL/bin/
+      mv -v hugo-completion $SNAPCRAFT_PART_INSTALL/
+      echo " * Stripping binary..."
+      ls -l $SNAPCRAFT_PART_INSTALL/bin/hugo
       strip --remove-section=.comment --remove-section=.note $SNAPCRAFT_PART_INSTALL/bin/hugo
-      mv hugo-completion $SNAPCRAFT_PART_INSTALL/hugo-completion
+      ls -l $SNAPCRAFT_PART_INSTALL/bin/hugo
     after: [go]
   go:
     source-tag: go1.10.3