chore(ci): Update openSUSE Leap 15.5 to 15.6

openSUSE Leap 15.5 has been deprecated since December of 2024.

Version 15.6 is the newest and support is expected until December of 2025.

Author: guihkx

.github/workflows/linux.yml

@@ -112,7 +112,7 @@ jobs:
             build-type: release
 
           # openSUSE's release cycle: https://endoflife.date/opensuse
-          - image: opensuse-15_5
+          - image: opensuse-15_6
             build-script: rpm_entrypoint.sh
             build-type: release
     steps:

Dockerfiles/opensuse-15_5 renamed to Dockerfiles/opensuse-15_6

@@ -1,7 +1,7 @@
 # vim: set syntax=dockerfile:
-FROM opensuse/leap:15.5
+FROM opensuse/leap:15.6
 
-LABEL org.opencontainers.image.description="Base image used to build and RPM-package Notes on openSUSE 15.5"
+LABEL org.opencontainers.image.description="Base image used to build and RPM-package Notes on openSUSE 15.6"
 
 # Install dependencies.
 RUN zypper install -y --no-recommends cmake gcc10-c++ git \
@@ -12,6 +12,9 @@ RUN zypper install -y --no-recommends cmake gcc10-c++ git \
 ENV CC=gcc-10
 ENV CXX=g++-10
 
+# Silences locale-related warnings from AutoUic.
+ENV LANG=C.UTF-8
+
 # Prevent a fatal error from git: "detected dubious ownership in repository at '/src'".
 RUN git config --global --add safe.directory /src