Bump the platform default up to C17.

This is already the "default default" for gcc and clang.

Bug: http://b/232413369
Test: treehugger
Change-Id: I3c0df7c63e8fca1b7692ad867d349a645559c209
diff --git a/cc/config/global.go b/cc/config/global.go
index d63e324..8ff5f55 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -298,9 +298,9 @@
 		"-w",
 	}
 
-	CStdVersion               = "gnu11"
+	CStdVersion               = "gnu17"
 	CppStdVersion             = "gnu++17"
-	ExperimentalCStdVersion   = "gnu17"
+	ExperimentalCStdVersion   = "gnu2x"
 	ExperimentalCppStdVersion = "gnu++2a"
 
 	// prebuilts/clang default settings.