add missing mips option

Refer to https://golang.org/doc/install/source#environment and
https://goreleaser.com/customization/#Builds, add `hardfloat` as
default.

Signed-off-by: Xiang Dai <764524258@qq.com>

.goreleaser.yml

@@ -25,6 +25,8 @@ builds:
     goarm:
       - 6
       - 7
+    gomips:
+      - hardfloat
     env:
       - CGO_ENABLED=0
     main: ./cmd/golangci-lint/