build: add release-install goal, hash individual binaries

We add a new make goal called release-install that creates the same
reproducible binaries as the release script would create, but only for
the current OS/architecture. It then installs those binaries to the
system's GOBIN directory.
To allow easy verification of individual binaries (instead of just the
packag tarballs/zips), we also add the hashes of lnd and lncli binaries
to the manifest. We do the same in the docker build.

scripts/release.sh

@@ -181,6 +181,10 @@ function build_release() {
     env CGO_ENABLED=0 GOOS=$os GOARCH=$arch GOARM=$arm go build -v -trimpath -ldflags="${ldflags}" -tags="${buildtags}" ${PKG}/cmd/lncli
     popd
 
+    # Add the hashes for the individual binaries as well for easy verification
+    # of a single installed binary.
+    sha256sum "${dir}/"* >> "manifest-$tag.txt" 
+
     if [[ $os == "windows" ]]; then
       reproducible_zip "${dir}"
     else
@@ -188,7 +192,10 @@ function build_release() {
     fi
   done
 
-  sha256sum * >manifest-$tag.txt
+  # Add the hash of the packages too, then sort by the second column (name).
+  sha256sum lnd-* vendor* >> "manifest-$tag.txt"
+  LC_ALL=C sort -k2 -o "manifest-$tag.txt" "manifest-$tag.txt"
+  cat "manifest-$tag.txt"
 }
 
 # usage prints the usage of the whole script.