testing/gyp: use python3

7 jobs for !711 with gyp in 58 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
passed lint #7466
docker-alpine x86_64

00:00:23

 
  Build
passed build-aarch64 #7471
docker-alpine ci-build aarch64

00:00:26

passed build-armv7 #7472
docker-alpine ci-build armv7

00:00:30

passed build-ppc64le #7470
docker-alpine ci-build ppc64le

00:00:32

passed build-s390x #7469
docker-alpine ci-build s390x

00:00:23

passed build-x86 #7468
ci-build x86 docker-alpine

00:00:28

passed build-x86_64 #7467
docker-alpine ci-build x86_64

00:00:32