[dev.cc] runtime: explicitly exclude android in zgoos_linux.go

Otherwise both zgoos_linux.go and zgoos_android.go will be compiled
for GOOS=android.

LGTM=crawshaw, rsc
R=rsc, crawshaw
CC=golang-codereviews
https://golang.org/cl/178110043

src/runtime/gengoos.go

@@ -46,7 +46,9 @@ func main() {
 	for _, target := range gooses {
 		var buf bytes.Buffer
 		fmt.Fprintf(&buf, "// generated by gengoos.go using 'go generate'\n\n")
-		fmt.Fprintf(&buf, "// +build %s\n\n", target) // usually redundant, but not always; see linux vs android
+		if target == "linux" {
+			fmt.Fprintf(&buf, "// +build !android\n\n") // must explicitly exclude android for linux
+		}
 		fmt.Fprintf(&buf, "package runtime\n\n")
 		fmt.Fprintf(&buf, "const theGoos = `%s`\n\n", target)
 		for _, goos := range gooses {

src/runtime/zgoos_android.go

 // generated by gengoos.go using 'go generate'
 
-// +build android
-
 package runtime
 
 const theGoos = `android`

src/runtime/zgoos_darwin.go

 // generated by gengoos.go using 'go generate'
 
-// +build darwin
-
 package runtime
 
 const theGoos = `darwin`

src/runtime/zgoos_dragonfly.go

 // generated by gengoos.go using 'go generate'
 
-// +build dragonfly
-
 package runtime
 
 const theGoos = `dragonfly`

src/runtime/zgoos_freebsd.go

 // generated by gengoos.go using 'go generate'
 
-// +build freebsd
-
 package runtime
 
 const theGoos = `freebsd`

src/runtime/zgoos_linux.go

 // generated by gengoos.go using 'go generate'
 
-// +build linux
+// +build !android
 
 package runtime
 

src/runtime/zgoos_nacl.go

 // generated by gengoos.go using 'go generate'
 
-// +build nacl
-
 package runtime
 
 const theGoos = `nacl`

src/runtime/zgoos_netbsd.go

 // generated by gengoos.go using 'go generate'
 
-// +build netbsd
-
 package runtime
 
 const theGoos = `netbsd`

src/runtime/zgoos_openbsd.go

 // generated by gengoos.go using 'go generate'
 
-// +build openbsd
-
 package runtime
 
 const theGoos = `openbsd`

src/runtime/zgoos_plan9.go

 // generated by gengoos.go using 'go generate'
 
-// +build plan9
-
 package runtime
 
 const theGoos = `plan9`

src/runtime/zgoos_solaris.go

 // generated by gengoos.go using 'go generate'
 
-// +build solaris
-
 package runtime
 
 const theGoos = `solaris`

src/runtime/zgoos_windows.go

 // generated by gengoos.go using 'go generate'
 
-// +build windows
-
 package runtime
 
 const theGoos = `windows`