GitLab CI: avoid calling before_scripts on unintended jobs

At this point it seems that all jobs depend on those steps, with
maybe the EDK2 jobs as exceptions.

The jobs that will be added later will not want those scripts to be
run, so let's move these steps to the appropriate jobs, while
still trying to avoid repetition.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Message-Id: <20200525131823.715-4-thuth@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
[thuth: Rebased to current master branch, use separate template]
Signed-off-by: Thomas Huth <thuth@redhat.com>

.gitlab-ci.yml

@@ -2,11 +2,13 @@ include:
   - local: '/.gitlab-ci-edk2.yml'
   - local: '/.gitlab-ci-opensbi.yml'
 
-before_script:
- - apt-get update -qq
- - apt-get install -y -qq libglib2.0-dev libpixman-1-dev genisoimage
+.update_apt_template: &before_script_apt
+ before_script:
+  - apt-get update -qq
+  - apt-get install -y -qq libglib2.0-dev libpixman-1-dev genisoimage
 
 build-system1:
+ <<: *before_script_apt
  script:
  - apt-get install -y -qq libgtk-3-dev libvte-dev nettle-dev libcacard-dev
       libusb-dev libvde-dev libspice-protocol-dev libgl1-mesa-dev libvdeplug-dev
@@ -19,6 +21,7 @@ build-system1:
  - make -j2 check
 
 build-system2:
+ <<: *before_script_apt
  script:
  - apt-get install -y -qq libsdl2-dev libgcrypt-dev libbrlapi-dev libaio-dev
       libfdt-dev liblzo2-dev librdmacm-dev libibverbs-dev libibumad-dev
@@ -32,6 +35,7 @@ build-system2:
  - make -j2 check
 
 build-disabled:
+ <<: *before_script_apt
  script:
  - mkdir build
  - cd build
@@ -46,6 +50,7 @@ build-disabled:
  - make -j2 check-qtest SPEED=slow
 
 build-tcg-disabled:
+ <<: *before_script_apt
  script:
  - apt-get install -y -qq clang libgtk-3-dev libusb-dev
  - mkdir build
@@ -64,6 +69,7 @@ build-tcg-disabled:
             260 261 262 263 264 270 272 273 277 279
 
 build-user:
+ <<: *before_script_apt
  script:
  - mkdir build
  - cd build
@@ -73,6 +79,7 @@ build-user:
  - make run-tcg-tests-i386-linux-user run-tcg-tests-x86_64-linux-user
 
 build-clang:
+ <<: *before_script_apt
  script:
  - apt-get install -y -qq clang libsdl2-dev libattr1-dev libcap-ng-dev
       xfslibs-dev libiscsi-dev libnfs-dev libseccomp-dev gnutls-dev librbd-dev
@@ -85,6 +92,7 @@ build-clang:
  - make -j2 check
 
 build-tci:
+ <<: *before_script_apt
  script:
  - TARGETS="aarch64 alpha arm hppa m68k microblaze moxie ppc64 s390x x86_64"
  - mkdir build