Revert "fix errors when Limes is built outside GOPATH"

This reverts commit 6c1fd2c,
because it breaks normal operation due to
<golang/go#17451>.

Makefile

@@ -13,11 +13,11 @@ build/limes: FORCE
 	$(GO) install $(GO_BUILDFLAGS) -ldflags '$(GO_LDFLAGS)' '$(PKG)'
 
 # which packages to test with static checkers?
-GO_ALLPKGS := $(PKG) $(shell $(GO) list $(PKG)/pkg/...)
+GO_ALLPKGS := $(PKG) $(shell go list $(PKG)/pkg/...)
 # which packages to test with `go test`?
-GO_TESTPKGS := $(shell $(GO) list -f '{{if .TestGoFiles}}{{.ImportPath}}{{end}}' $(PKG)/pkg/...)
+GO_TESTPKGS := $(shell go list -f '{{if .TestGoFiles}}{{.ImportPath}}{{end}}' $(PKG)/pkg/...)
 # which packages to measure coverage for?
-GO_COVERPKGS := $(shell $(GO) list $(PKG)/pkg/... | grep -v plugins)
+GO_COVERPKGS := $(shell go list $(PKG)/pkg/... | grep -v plugins)
 # output files from `go test`
 GO_COVERFILES := $(patsubst %,build/%.cover.out,$(subst /,_,$(GO_TESTPKGS)))