Ignore go build failure in makefile

[dfilipovic39]

Hi,
there seems to be a problem when you modify go code, and makefile tries to rebuild server. If there is any compile time error the makefile recipe crashes.

Possible soultion would be prefixing build command with - :
-@go build -ldflags '$(LDFLAGS)' -o $@ $(IMPORT_PATH)/server

Failed build will be ignored this way and old binary would be used

[olebedev]

Hi @tarqe39,

thank you for the suggestion! BTW, pull requests are welcome.