gitlab: force enable docs build in Fedora, Ubuntu, Debian

Meson runs a test to see if Sphinx works, and automatically disables it
on error. This can lead to the CI jobs skipping docs build without
maintainers noticing the problem. Use --enable-docs to force a fatal
error if Sphinx doesn't work on the jobs where we expect it to be OK.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20201102130926.161183-3-berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

.gitlab-ci.yml

@@ -74,6 +74,7 @@ build-system-ubuntu:
     TARGETS: aarch64-softmmu alpha-softmmu cris-softmmu hppa-softmmu
       moxie-softmmu microblazeel-softmmu mips64el-softmmu
     MAKE_CHECK_ARGS: check-build
+    CONFIGURE_ARGS: --enable-docs
   artifacts:
     expire_in: 2 days
     paths:
@@ -105,6 +106,7 @@ build-system-debian:
     TARGETS: arm-softmmu avr-softmmu i386-softmmu mipsel-softmmu
       riscv64-softmmu sh4eb-softmmu sparc-softmmu xtensaeb-softmmu
     MAKE_CHECK_ARGS: check-build
+    CONFIGURE_ARGS: --enable-docs
   artifacts:
     expire_in: 2 days
     paths:
@@ -133,7 +135,7 @@ build-system-fedora:
   <<: *native_build_job_definition
   variables:
     IMAGE: fedora
-    CONFIGURE_ARGS: --disable-gcrypt --enable-nettle
+    CONFIGURE_ARGS: --disable-gcrypt --enable-nettle --enable-docs
     TARGETS: tricore-softmmu microblaze-softmmu mips-softmmu
       xtensa-softmmu m68k-softmmu riscv32-softmmu ppc-softmmu sparc64-softmmu
     MAKE_CHECK_ARGS: check-build