add Windows option; rearrange commands

Author: David Coe

go/adbc/pkg/Makefile

@@ -21,14 +21,16 @@ RM := rm -f
 
 ifeq ($(shell go env GOOS),linux)
 	SUFFIX=so
+	GIT_VERSION=$(shell git tag --sort=-v:refname --points-at $(shell git rev-list --tags --max-count=1 2>/dev/null) 2>/dev/null | head -n 1)
 else ifeq ($(shell go env GOOS),windows)
 	SUFFIX=dll
 	RM=del
+	GIT_VERSION=$(shell powershell -Command "git tag --sort=-v:refname --points-at $(git rev-list --tags --max-count=1) | Select-Object -First 1")
 else
 	SUFFIX=dylib
 endif
 
-GIT_VERSION=$(shell git tag -l --points-at $(shell git rev-list --tags --max-count=1) --sort=-v:refname | head -n 1)
+GIT_VERSION ?= unknown
 VERSION=$(subst go/adbc/,,$(GIT_VERSION))
 
 # Expand dynamically libadbc_driver_.SUFFIX