ci: set GIT_SUBMODULE_STRATEGY to none where not submodules are not needed

I've decided to omit some places (e.g. build crypto) where it might be
confusing if some submodules dependency is introduced. Well, that
concerns tests stages as well, but I guess it is more likely for the
build stage.

Updates #108

ci/core.yml

@@ -29,6 +29,8 @@ build core unix:
 
 test core unix unit:
   stage: test
+  variables:
+    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   dependencies:
     - build core unix
   script:
@@ -37,6 +39,8 @@ test core unix unit:
 
 test core unix device:
   stage: test
+  variables:
+    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   dependencies:
     - build core unix
   script:
@@ -45,6 +49,8 @@ test core unix device:
 
 test core unix monero:
   stage: test
+  variables:
+    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   dependencies:
     - build core unix
   script:

ci/environment.yml

@@ -2,6 +2,7 @@ environment:
   stage: environment
   image: docker:latest
   variables:
+    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
     CONTAINER_NAME: "$CI_REGISTRY/trezor/trezor-firmware/environment"
   services:
     - docker:dind

ci/legacy.yml

@@ -44,6 +44,8 @@ build legacy emu:
 
 # TODO: aren't some tests from .travis.yml missing?
 test legacy emu:
+  variables:
+    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   stage: test
   dependencies:
     - build legacy emu

ci/storage.yml

@@ -1,6 +1,8 @@
 image: registry.corp.sldev.cz/trezor/trezor-firmware/environment
 
 test storage:
+  variables:
+    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   stage: test
   dependencies: []
   script: