cmd/cgo: add required gcc flags for GOARCH=mips{,le}

Change-Id: I1d6a2120a444d1ab9b9ecfdf27464325ad741d55
Reviewed-on: https://go-review.googlesource.com/34315Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/cgo/gcc.go

@@ -1210,6 +1210,8 @@ func (p *Package) gccMachine() []string {
 		return []string{"-m64"}
 	case "mips64", "mips64le":
 		return []string{"-mabi=64"}
+	case "mips", "mipsle":
+		return []string{"-mabi=32"}
 	}
 	return nil
 }

src/cmd/go/build.go

@@ -3220,6 +3220,8 @@ func (b *builder) gccArchArgs() []string {
 		return []string{"-m64", "-march=z196"}
 	case "mips64", "mips64le":
 		return []string{"-mabi=64"}
+	case "mips", "mipsle":
+		return []string{"-mabi=32", "-march=mips32"}
 	}
 	return nil
 }