util/ide-config.sh: Bump C standard to C18

Enable C18 syntax in vscode cpptools.
This is important because we use some backward incompatible c18
syntax in EC. This syntax is not properly recognized when c11 mode
is used.

VSCode CPPTools now supports C18.
https://github.com/microsoft/vscode-cpptools/releases/tag/0.28.0

BRANCH=none
BUG=none
TEST=none

Signed-off-by: Craig Hesling <hesling@chromium.org>
Change-Id: I3e508f6d0e121e872476ca32db89d6abbbc8ff6c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2218458
Commit-Queue: Jett Rink <jettrink@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>

util/ide-config.sh

@@ -230,9 +230,8 @@ vscode() {
 
 				echo '"compilerPath": "/usr/bin/arm-none-eabi-gcc",'
 				# echo '"compilerArgs": [],'
-				# The macro __STDC_VERSION__ is 201710L,
-				# which is c18. The closest is c11.
-				echo '"cStandard": "c11",'
+				# The macro __STDC_VERSION__ is 201710L, which corresponds to c18.
+				echo '"cStandard": "c18",'
 				# echo '"cppStandard": "c++17",'
 				echo '"intelliSenseMode": "gcc-x64"'
 			} | {