Allow VER to be overridden (e.g., for building from non-clone source)

skeleton

@@ -2,7 +2,7 @@ PROGNM = programname
 
 CC ?= gcc
 CFLAGS ?= -O2 -fPIE -flto -fstack-protector-strong --param=ssp-buffer-size=1 -Wno-reserved-id-macro -Wall -Wextra -Wpedantic -Werror -std=c18
-VER = `git describe --long --tags | sed 's/\([^-]*-g\)/r\1/;s/-/./g'`
+VER ?= $(shell (git describe --long --tags | sed 's/\([^-]*-g\)/r\1/;s/-/./g') || date +"v0.r%Y%m%d")
 FMFLAGS = -wp -then -wp -wp-rte
 SOURCES ?= $(wildcard src/*.c)
 ARCH ?= $(shell uname -m)