glib: put the expected python in $PATH
On testnodes, python can be too long for linux shebang (#!) line.
We had for example:
/srv/slapgrid/slappart15/srv/testnode/cqc/inst/test0-0/tmp/shared/python2.7/338ccc0e387d64185920266f8a97c87b/bin/python2.7that is 123 characters long.
With this, the generated glib-genmarshal script will have:
#!/usr/bin/env /srv/slapgrid/slappart15/srv/testnode/cqc/inst/test0-0/tmp/shared/python2.7/338ccc0e387d64185920266f8a97c87b/bin/python2.7which exceeds the linux kernel limit.
Instead, we generate scripts that will use
#!/usr/bin/env pythonand it will be the caller responsibility to set $PATH to use the expected python.
This fixes the issues we had on SlapOS.SoftwareReleases.IntegrationTest tests since we updated glib to 2.56.4 in a7a86db9