build: Always pass ldflags to builds on OSX

Previously, 'ldflags' were added to the compiler invocation based on the
version of Go the user was running. It seems to make more sense to
simply always pass along the flags on Darwin (due to the bug mentioned
in the comment above this line in the diff) as that is less brittle than
branching on the Go version, and yet will not break current users /
developers work flow.

Makefile

@@ -9,7 +9,7 @@ GOVERSION=$(shell go version)
 # will be malformed once we codesign it and
 # unable to execute.
 # See https://github.com/golang/go/issues/11887#issuecomment-126117692.
-ifneq (,$(findstring 1.5, $(GOVERSION)))
+ifeq "$(UNAME)" "Darwin"
 	FLAGS=-ldflags="-s"
 endif