gitlab-ci: get the location of the fossils.yml via a command

The rationale for this is that we would like to have "private" runners
which would be using "private" fossils-db repositories.

This way, for example, we can have jobs that will exercise non public
fossils but, still, we will have their result in the upstream
pipeline.

Signed-off-by: Andres Gomez <agomez@igalia.com>
Status Job ID Name Coverage
  Container
manual #2435699
aarch64 manual
arm_build
manual #2435701
aarch64 manual
arm_test
manual #2435703
windows shell 1809 mesa manual
windows_build_vs2019
manual #2435692
manual
x86_build
manual #2435698
manual
x86_build_old
manual #2435694
manual
x86_test-gl
manual #2435696
manual
x86_test-vk
 
  Meson X86 64
created #2435711
meson-clang
created #2435709
meson-classic
created #2435712
meson-clover
created #2435714
meson-clover-old-llvm
created #2435707
meson-gallium
created #2435706
meson-testing
created #2435716
meson-vulkan
 
  Scons
created #2435717
allowed to fail
scons-win64
 
  Meson Misc
created #2435721
aarch64
meson-arm64
created #2435723
aarch64
meson-arm64-build-test
created #2435719
aarch64
meson-armhf
created #2435728
meson-i386
created #2435733
meson-mingw32-x86_64
created #2435731
kvm
meson-ppc64el
created #2435729
kvm
meson-s390x
created #2435725
windows docker 1809 mesa
meson-windows-vs2019
 
  Llvmpipe
created #2435740
llvmpipe-gles2
created #2435742
llvmpipe-traces
created #2435737
piglit-glslparser
created #2435735
piglit-quick_gl
created #2435739
piglit-quick_shader
 
  Softpipe
created #2435744
softpipe-gles2
created #2435749
softpipe-gles31 1/4
created #2435746
softpipe-gles3 1/2
created #2435751
softpipe-gles31 2/4
created #2435752
softpipe-gles31 3/4
created #2435754
softpipe-gles31 4/4
created #2435747
softpipe-gles3 2/2
 
  Freedreno
created #2435763
google-freedreno-db410c
arm64_a306_gles2
created #2435764
google-freedreno-db820c
arm64_a530_gles2
created #2435756
mesa-cheza
arm64_a630_gles2
created #2435760
mesa-cheza
arm64_a630_gles3
created #2435758
mesa-cheza
arm64_a630_gles31
 
  Panfrost
created #2435765
mesa-ci-aarch64-lava-collabora
panfrost-t720-gles2:arm64
created #2435766
mesa-ci-aarch64-lava-collabora
panfrost-t760-gles2:armhf
created #2435767
mesa-ci-aarch64-lava-collabora
panfrost-t860-gles2:arm64
created #2435768
mesa-ci-aarch64-lava-collabora
panfrost-t860-gles3:arm64
 
  Radv
created #2435769
radv-fossils
 
  Virgl
created #2435770
virgl-gles2
created #2435771
virgl-gles3
created #2435772
virgl-gles31
created #2435773
virgl-traces