cos-gpu-installer:v2.0.20 release

Releases change:
https://cos-review.googlesource.com/c/cos/tools/+/30822.

Adds --prepare-build-tools flag to gpu installer v2 which populates toolchain cache

BUG=b/175236375

Change-Id: Ie48dcfa748819d431a1aa2edecec0d91e94f6ac7
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/30982
Tested-by: Arnav Kansal <rnv@google.com>
Reviewed-by: Rayan Dasoriya <dasoriya@google.com>
Cloud-Build: GCB Service account <228075978874@cloudbuild.gserviceaccount.com>
diff --git a/release/release-versions.yaml b/release/release-versions.yaml
index 7406fac..0404c0f 100644
--- a/release/release-versions.yaml
+++ b/release/release-versions.yaml
@@ -18,6 +18,6 @@
     - "v20220314"
 - staging_container_name: "cos-gpu-installer"
   release_container_name: "cos-gpu-installer"
-  build_commit: "4e3f8b9f30ebeaccdfbd158ad6d5210c9f4f6131"
+  build_commit: "2cd0d648ba8db179b023b6bf44567009ee86b7a4"
   release_tags:
-    - "v2.0.19"
+    - "v2.0.20"