chg: test: Disable 'doh' unit test on Enterprise Linux 8

Disable test that fails for months on this platform.

Closes #5448

Merge branch '5448-disable-doh-unit-test-on-el8' into 'main'

See merge request isc-projects/bind9!11276

.gitlab-ci.yml

@@ -993,7 +993,6 @@ unit:gcc:almalinux8:amd64:
   needs:
     - job: gcc:almalinux8:amd64
       artifacts: true
-  allow_failure: true  # remove once GL#5448 is fixed
 
 # Jobs for regular GCC builds on Alma Linux 9 (amd64)
 

tests/isc/meson.build

@@ -60,7 +60,9 @@ flaky_isc_test = [
     'proxystream',
 ]
 
-if config.has('HAVE_LIBNGHTTP2')
+is_el8 = run_command('grep', '-q', '-F', 'platform:el8', '/etc/os-release', check: false).returncode() == 0
+
+if config.has('HAVE_LIBNGHTTP2') and not is_el8
     isc_test += 'doh'
 endif