Revert "Bump the global default C standard to gnu23."

This reverts commit 90b3357c40ae4697c6c0d2ab95575aa367742129.

Reason for revert: DroidMonitor: Potential culprit for http://b/395891989#comment5 - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Change-Id: I7757a612910e760b4ca6f98c4fd1f208e430a5ca
diff --git a/cc/cc_test.go b/cc/cc_test.go
index 2be4e48..98af7b6 100644
--- a/cc/cc_test.go
+++ b/cc/cc_test.go
@@ -2689,7 +2689,7 @@
 	cppOnly := []string{"-fPIC", "${config.CommonGlobalCppflags}", "${config.DeviceGlobalCppflags}", "${config.ArmCppflags}"}
 
 	cflags := []string{"-Werror", "-std=candcpp"}
-	cstd := []string{"-std=gnu23", "-std=conly"}
+	cstd := []string{"-std=gnu17", "-std=conly"}
 	cppstd := []string{"-std=gnu++20", "-std=cpp", "-fno-rtti"}
 
 	lastNDKFlags := []string{