Fix skaffold debug for helm charts with skaffold config file other than default skaffold.yaml

[tejal29]

Fixes #5133

Add SKAFFOLD_FILENAME environment variable while debugging so --post-renderer skaffold can run successfully.

Before on master

cd examples/helm-deployment && mv skaffold.yaml test.yaml
skaffold  -f test.yaml debug
Helm release skaffold-helm not installed. Installing...
Error: error while running post render on files: error while running command /Users/tejaldesai/Downloads/google-cloud-sdk2/bin/skaffold. error output:
skaffold config file skaffold.yaml not found - check your current working directory, or try running `skaffold init`
: exit status 1
exiting dev mode because first deploy failed: install: exit status 1

On branch,

 ../../out/skaffold -f test.yaml debug 
Tags used in deployment:
 - skaffold-helm -> skaffold-helm:a31ad23b8173b820bccafe6d15a75155be1862b564d214d8be5735ad045ff71c
Starting deploy...
Helm release skaffold-helm not installed. Installing...
NAME: skaffold-helm
LAST DEPLOYED: Fri Dec 11 09:52:51 2020
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
Waiting for deployments to stabilize...
 - deployment/skaffold-helm: waiting for rollout to finish: 0 of 1 updated replicas are available...
 - deployment/skaffold-helm is ready.
Deployments stabilized in 6.214218497s
Press Ctrl+C to exit
Not watching for changes...
[install-go-debug-support] Installing runtime debugging support files in /dbg
[install-go-debug-support] Installation complete
[skaffold-helm] API server listening at: [::]:56268

[codecov]

Codecov Report

Merging #5138 (d388ed0) into master (a999ca8) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5138      +/-   ##
==========================================
- Coverage   72.19%   72.16%   -0.04%     
==========================================
  Files         381      381              
  Lines       13543    13567      +24     
==========================================
+ Hits         9777     9790      +13     
- Misses       3050     3060      +10     
- Partials      716      717       +1     

Impacted Files	Coverage Δ
pkg/skaffold/deploy/helm/deploy.go	71.77% <100.00%> (+0.27%)	⬆️
pkg/skaffold/instrumentation/meter.go	64.51% <0.00%> (-12.41%)	⬇️
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
pkg/skaffold/runner/runcontext/context.go	84.61% <0.00%> (+1.28%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a999ca8...d388ed0. Read the comment docs.

[MarlonGamez]

lgtm 👍🏼