cerbero: Fix circular imports in shell.py

Import cerbero.hacks inside the function call that needs it to avoid
a top-level circular dependency in the importing. This is not
a problem right now, but it's a ticking time-bomb.
15 jobs for dont-use-tar-on-windows-ffs in 201 minutes and 55 seconds (queued for 1 second)
Status Job ID Name Coverage
  Preparation
passed #376252
manifest

00:00:19

 
  Pre Build
passed #376254
cerbero deps android universal

00:59:00

passed #376253
cerbero deps fedora x86_64

00:32:42

passed #376258
gst-ios-12.2
cerbero deps ios universal

02:31:06

passed #376257
gst-macos-10.14
cerbero deps macos x86_64

00:53:52

passed #376255
cerbero deps windows x86

00:47:52

passed #376256
cerbero deps windows x86_64

00:49:42

 
  Build
passed #376260
cerbero android universal

00:09:53

passed #376261
cerbero cross win32

00:07:33

passed #376262
cerbero cross win64

00:06:23

passed #376259
cerbero fedora x86_64

00:05:06

passed #376433
gst-ios-12.2
cerbero ios universal

00:33:41

passed #376263
gst-macos-10.14
cerbero macos x86_64

00:08:20

failed #376264
gst-ios-12.2
cerbero ios universal

00:38:55

 
  Integrate
passed #376265
cerbero android universal examples

00:06:52