fix google-cloud-sdk build

Change the way to import a Cloud SDK GPG key.

This is needed to fix build issues caused by
W: GPG error: https://packages.cloud.google.com/apt cloud-sdk InRelease:
The following signatures couldn't be verified because the public key is
not available: NO_PUBKEY B53DC80D13EDEF05

Change-Id: Ie45834b9611e605ae13e197dec0d315b5a1920e5
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/67154
Tested-by: Arnav Kansal <rnv@google.com>
Cloud-Build: GCB Service account <228075978874@cloudbuild.gserviceaccount.com>
Reviewed-by: Shuo Yang <gshuoy@google.com>
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
diff --git a/src/cmd/cos_kdump_debugger/Dockerfile b/src/cmd/cos_kdump_debugger/Dockerfile
index 5792724..60f99a0 100644
--- a/src/cmd/cos_kdump_debugger/Dockerfile
+++ b/src/cmd/cos_kdump_debugger/Dockerfile
@@ -14,8 +14,8 @@
     https://packages.cloud.google.com/apt cloud-sdk main" | \
     tee -a /etc/apt/sources.list.d/google-cloud-sdk.list && \
     curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | \
-    apt-key --keyring /usr/share/keyrings/cloud.google.gpg add - \
-    && apt-get update && apt-get -y -qq install google-cloud-sdk=369.0.0-0 && apt-get clean
+    gpg --dearmor -o /usr/share/keyrings/cloud.google.gpg && \
+    apt-get update && apt-get -y -qq install google-cloud-sdk && apt-get clean
 
 COPY ./kdump_debugger.sh /kdump_debugger.sh
 
diff --git a/src/cmd/cos_kernel_devenv/Dockerfile b/src/cmd/cos_kernel_devenv/Dockerfile
index e416aa3..12de174 100644
--- a/src/cmd/cos_kernel_devenv/Dockerfile
+++ b/src/cmd/cos_kernel_devenv/Dockerfile
@@ -6,8 +6,8 @@
 	apt-get -y install apt-transport-https ca-certificates gnupg curl && \
 	echo "deb [signed-by=/usr/share/keyrings/cloud.google.gpg] https://packages.cloud.google.com/apt cloud-sdk main" \
 	    > /etc/apt/sources.list.d/google-cloud-sdk.list && \
-	curl -o /usr/share/keyrings/cloud.google.gpg \
-	    https://packages.cloud.google.com/apt/doc/apt-key.gpg && \
+	curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | \
+	gpg --dearmor -o /usr/share/keyrings/cloud.google.gpg && \
 	apt-get update -y && \
 	DEBIAN_FRONTEND=noninteractive TZ=Etc/UTC apt-get install -y tzdata && \
 	apt-get install -y make python3 git libssl-dev bc bison flex cpio kmod \
diff --git a/src/cmd/toolbox/Dockerfile b/src/cmd/toolbox/Dockerfile
index c527ede..4f62693 100644
--- a/src/cmd/toolbox/Dockerfile
+++ b/src/cmd/toolbox/Dockerfile
@@ -20,8 +20,8 @@
     https://packages.cloud.google.com/apt cloud-sdk main" | \
     tee -a /etc/apt/sources.list.d/google-cloud-sdk.list && \
     curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | \
-    apt-key --keyring /usr/share/keyrings/cloud.google.gpg add - \
-    && apt-get update && apt-get -y -qq install google-cloud-sdk && apt-get clean
+    gpg --dearmor -o /usr/share/keyrings/cloud.google.gpg && \
+    apt-get update && apt-get -y -qq install google-cloud-sdk && apt-get clean
 
 # Various networking and other tools. net-tools installs arp, netstat, etc.
 RUN apt-get install -u -qq vim \