Update linux-x86 Go prebuilts from ab/9878432

https://ci.android.com/builds/branches/aosp-build-tools-release/grid?head=9878432&tail=9878432

Update script: toolchain/go/update-prebuilts.sh

Test: Treehugger presubmit
Change-Id: I07818c960e04b2ef4373ab22161590b088582d39
diff --git a/src/runtime/export_unix_test.go b/src/runtime/export_unix_test.go
index a548cf7..71a55d8 100644
--- a/src/runtime/export_unix_test.go
+++ b/src/runtime/export_unix_test.go
@@ -9,7 +9,6 @@
 import "unsafe"
 
 var NonblockingPipe = nonblockingPipe
-var Closeonexec = closeonexec
 
 func sigismember(mask *sigset, i int) bool {
 	clear := *mask
@@ -90,3 +89,9 @@
 func SendSigusr1(mp *M) {
 	signalM(mp, _SIGUSR1)
 }
+
+const (
+	O_WRONLY = _O_WRONLY
+	O_CREAT  = _O_CREAT
+	O_TRUNC  = _O_TRUNC
+)