gsutil: Remove trailing slashes, rsync instead of cp

[tstromberg]

Fixes #5605

Test output:

$ gsutil -m rsync -dJ out gs://minikube-builds/mystery-test
Building synchronization state...
Starting synchronization...
Copying file://out/coverage.txt [Content-Type=text/plain]...
Copying file://out/minikube [Content-Type=application/octet-stream]...          
Copying file://out/minikube-linux-amd64 [Content-Type=application/octet-stream]...
Copying file://out/gvisor-addon [Content-Type=application/octet-stream]...
/ [4/4 files][137.6 MiB/137.6 MiB] 100% Done                                    
Operation completed over 4 objects/137.6 MiB.                                    

$ gsutil -m rsync -dJ out gs://minikube-builds/mystery-test
Building synchronization state...
Starting synchronization...

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[codecov-io]

Codecov Report

Merging #5620 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5620   +/-   ##
=======================================
  Coverage   36.89%   36.89%           
=======================================
  Files         102      102           
  Lines        7369     7369           
=======================================
  Hits         2719     2719           
  Misses       4297     4297           
  Partials      353      353

[medyagh]

@tstromberg while we are at it, do you mind adding this to the common.sh
to make sure we SEE that we are runnining the right commit ID

echo ">> Starting ${E2E_BIN} at $(date)"
echo ">> The minikube version & commit id:"
echo $(out/minikube-${OS_ARCH} version)

you can even go one step further and grep echo $(out/minikube-${OS_ARCH} version) for ${COMMIT} env var to see if it is the same with the one in Jenkins

[tstromberg]

@tstromberg while we are at it, do you mind adding this to the common.sh
to make sure we SEE that we are runnining the right commit ID

echo ">> Starting ${E2E_BIN} at $(date)"
echo ">> The minikube version & commit id:"
echo $(out/minikube-${OS_ARCH} version)

you can even go one step further and grep echo $(out/minikube-${OS_ARCH} version) for ${COMMIT} env var to see if it is the same with the one in Jenkins

Will do so in a separate PR.