Remove BUILDARCH from the Makefile (closes #107)

The Makefile passed the build architecture in through
-X main.Buildarch, but no Buildarch variable exists in the code, so
the flag set nothing. The architecture is available at run time from
runtime.GOARCH and does not need to be passed in at build time.

Model: opus-5-5

Makefile

@@ -2,8 +2,7 @@
 
 BINARY := neoircd
 VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
-BUILDARCH := $(shell go env GOARCH)
+LDFLAGS := -X main.Version=$(VERSION)
-LDFLAGS := -X main.Version=$(VERSION) -X main.Buildarch=$(BUILDARCH)
 
 all: check build