Adjust nfpm config for bindir removal

See https://github.com/goreleaser/nfpm/pull/142#issuecomment-634427333

ci/build/build-packages.sh

@@ -21,7 +21,7 @@ main() {
     fi
   fi
 
-  if [[ $OSTYPE == linux* ]]; then
+  if [[ $OS == "linux" ]]; then
     release_nfpm
   fi
 }
@@ -48,7 +48,7 @@ release_gcp() {
 # Generates deb and rpm packages.
 release_nfpm() {
   local nfpm_config
-  nfpm_config=$(envsubst < ./ci/build/nfpm.yaml)
+  nfpm_config="$(envsubst < ./ci/build/nfpm.yaml)"
 
   # The underscores are convention for .deb.
   nfpm pkg -f <(echo "$nfpm_config") --target "release-packages/code-server_${VERSION}_$ARCH.deb"