website: Changed clang documentation

Updated the website to reflect that gem5
now supports up to Clang version 9.

Jira: https://gem5.atlassian.net/browse/GEM5-394
Change-Id: Ie06d67194ac875b9cbe9f80f8667e4546f00e0dd
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/28894
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: Jason Lowe-Power <power.jg@gmail.com>
diff --git a/_pages/documentation/general_docs/building/index.md b/_pages/documentation/general_docs/building/index.md
index 5b8948d..f68f4e3 100644
--- a/_pages/documentation/general_docs/building/index.md
+++ b/_pages/documentation/general_docs/building/index.md
@@ -49,8 +49,7 @@
 and [version >7 may be supported](https://gem5.atlassian.net/browse/GEM5-194)
 in future releases of gem5.
     * **Clang**: Clang can also be used. At present, we support Clang 3.9 to
-Clang 7 (inclusive). [Support for Clang >7 may be supported](
-https://gem5.atlassian.net/browse/GEM5-394) in future releases of gem5.
+Clang 9 (inclusive).
 * **SCons** : gem5 uses SCons as its build environment.
 * **Python** : gem5 relies on Python development libraries. As of gem5 version
 20, gem5 can be compiled and run in environments using either Python 2.7 or