Allow MOSCTL_BINARY and ZOT_BINARY to be read from the environment.

This allows user that invokes make to influence the mosctl
and zot binary via MOSCTL_BINARY and ZOT_BINARY variables respectively.

The make variables will take the values present in the environment
or on the make command line if provided.

So either:

    export MOSCTL_BINARY=/tmp/my-mosctl
    export ZOT_BINARY=http://...

or

    make MOSCTL_BINARY=... ZOT_BINARY=...

layers/mos/stacker.yaml

@@ -8,8 +8,10 @@ mos-build:
     type: built
     tag: build-krd
   import:
-    - ${{MOSCTL_BINARY:https://github.com/project-machine/mos/releases/download/0.0.9/mosctl}}
-    - ${{ZOT_BINARY:https://github.com/project-zot/zot/releases/download/v1.4.3/zot-linux-amd64-minimal}}
+    - path: ${{MOSCTL_BINARY}}
+      dest: /imports/mosctl
+    - path: ${{ZOT_BINARY}}
+      dest: /imports/zot
     - zot-config.json
   run: |
     d=$(mktemp -d)
@@ -23,10 +25,10 @@ mos-build:
     cp /stacker/zot-config.json "$workd/etc/"
 
     mkdir -p "$workd/usr/bin"
-    for bin in mosctl:mosctl zot-linux-amd64-minimal:zot ; do
-      t=$workd/usr/bin/${bin#*:}
-      cp -v /stacker/${bin%:*} $t
-      chmod 755 $t
+    for bin in mosctl zot; do
+      t="$workd/usr/bin/$bin"
+      cp -v /imports/${bin} "$t"
+      chmod 755 "$t"
     done
 
     # dracut-install will pick up all the deps for these binaries

subs.mk

@@ -2,11 +2,15 @@ KEYSET ?= snakeoil
 DOCKER_BASE ?= docker://
 UBUNTU_MIRROR ?= http://archive.ubuntu.com/ubuntu
 KEYSET_D ?= $(HOME)/.local/share/machine/trust/keys/$(KEYSET)
+MOSCTL_BINARY ?= https://github.com/project-machine/mos/releases/download/0.0.9/mosctl
+ZOT_BINARY ?= https://github.com/project-zot/zot/releases/download/v1.4.3/zot-linux-amd64-minimal
 
 STACKER_SUBS = \
 	--substitute=KEYSET_D=$(KEYSET_D) \
 	--substitute=DOCKER_BASE=$(DOCKER_BASE) \
 	--substitute=UBUNTU_MIRROR=$(UBUNTU_MIRROR) \
 	--substitute=HOME=$(HOME) \
 	--substitute=KEYS_DIR=$(HOME)/.local/share/machine/trust/keys \
-	--substitute=TOP_D=$(TOP_D)
+	--substitute=TOP_D=$(TOP_D) \
+	--substitute=MOSCTL_BINARY=$(MOSCTL_BINARY) \
+	--substitute=ZOT_BINARY=$(ZOT_BINARY)