Update .gitlab-ci.yml to be explicit about clang-10

11 jobs for gitlab-ci in 11 minutes and 24 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #687
build_alpine_gcc

00:00:52

passed #696
build_clang

00:03:24

passed #685
build_gcc

00:00:56

failed #686
build_clang

00:00:26

 
  Test
failed #690
test_list_alpine_gcc

00:01:52

passed #689
test_list_clang

00:01:54

passed #688
test_list_gcc

00:02:23

 
  Valgrindtest
skipped #691
test_valgrind_alpine_gcc
skipped #693
test_valgrind_clang
skipped #692
test_valgrind_gcc
 
  Scanbuild
skipped #694
scan_build
 
Name Stage Failure
failed
test_list_alpine_gcc Test
Test Summary Report
-------------------
unit/test_proto (Wstat: 0 Tests: 48 Failed: 2)
Failed tests: 13, 15
Files=19, Tests=3217, 51 wallclock secs ( 0.84 usr 0.29 sys + 7.57 cusr 1.00 csys = 9.70 CPU)
Result: FAIL
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1