mk/targets.mk: Fix ORGVERSION in tag-less repos

* mk/targets.mk (ORGVERSION, GITVERSION): trim "-dev" suffix from ORGVERSION.

61336f80 uses org.el's Version metadata to generate ORGVERSION when
the source repository has no tags.
This can result in an org-version of "Major.Minor-dev".
The "-dev" suffix is not recognized by `version-to-list' as a valid
version syntax because it is not part of `version-regexp-alist'.

mk/targets.mk

@@ -15,8 +15,8 @@ ifneq ($(wildcard .git),)
   ifeq ($(ORGVERSION),)
     # In elpa.git, there are no tags available.  Fall back to using
     # the org.el header.
-    ORGVERSION := $(shell $(BATCH) --eval "(require 'lisp-mnt)" \
-      --visit lisp/org.el --eval '(princ (lm-header "version"))')
+    ORGVERSION := $(patsubst %-dev,%,$(shell $(BATCH) --eval "(require 'lisp-mnt)" \
+      --visit lisp/org.el --eval '(princ (lm-header "version"))'))
     GITVERSION ?= $(ORGVERSION)-g$(shell git rev-parse --short=6 HEAD)
   else
     GITVERSION ?= $(shell git describe --match release\* --abbrev=6 HEAD)