Prevent the arm64 buster images to build the sqlsrv extension

Only bullseye has support for sqlsrv on arm64, so we need to
stop building the extension in this branch (for arm64).

- buster: https://packages.microsoft.com/debian/10/prod/pool/main/m/msodbcsql18/
- bullseye: https://packages.microsoft.com/debian/11/prod/pool/main/m/msodbcsql18/

Author: stronk7

root/tmp/setup/sqlsrv-extension.sh

@@ -2,6 +2,14 @@
 
 set -e
 
+# Debian buster (10) haven't got the arm64 packages, it seems, see:
+# - buster: https://packages.microsoft.com/debian/10/prod/pool/main/m/msodbcsql18/
+# So we won't build the extension for buster (10) images on arm64.
+if [[ ${TARGETPLATFORM} != "linux/amd64" ]]; then
+  echo "sqlsrv extension not available for ${TARGETPLATFORM} architecture, skipping"
+  exit 0
+fi
+
 # Packages for build.
 BUILD_PACKAGES="gnupg unixodbc-dev"