ci: fix code generation

With the recent bump to Golang 1.15, the code generation was broken.
Changing the output-base to the main repo and not the vendor solves the
issue and feel more natural too. The command "go mod vendor" only
cherry-picks certain files for inclusion  in the vendor folder. I
suspect the upgrade to Golang 1.15 introduced that behavior. Previously
our vendir dir was full and now it has nothing (from rook) that's why
the code generator was removing all our interfaces.

Signed-off-by: Sébastien Han <seb@redhat.com>

build/codegen/codegen.sh

@@ -19,11 +19,14 @@ GROUP_VERSIONS="rook.io:v1 rook.io:v1alpha2 ceph.rook.io:v1 nfs.rook.io:v1alpha1
 scriptdir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 codegendir="${scriptdir}/../../vendor/k8s.io/code-generator"
 
+# ensures the vendor dir has the right deps, e,g. code-generator
+go mod vendor
+
+# run code generation
 bash ${codegendir}/generate-groups.sh \
     all \
     github.com/rook/rook/pkg/client \
     github.com/rook/rook/pkg/apis \
     "${GROUP_VERSIONS}" \
-    --output-base "${scriptdir}/../../vendor" \
+    --output-base "$(dirname "${BASH_SOURCE[0]}")/../../.." \
     --go-header-file "${scriptdir}/boilerplate.go.txt"
-cp -r "${scriptdir}/../../vendor/github.com/rook/rook/pkg" "${scriptdir}/../../"