Release builds: rpm x86-64 and OpenWrt on ubuntu-24.04

ubuntu-latest is now 26.04. Its rpm 6 runs the signing command of
.rpmmacros without taking its second word as argv[0], so gpg got the
"gpg" there as a file name and every rpm of 1.0.2 failed to sign. The
OpenWrt 24.10 SDK refuses its install, which is not GNU's. arm64 already
builds on ubuntu-24.04-arm.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/build-ipk.yml

@@ -30,7 +30,8 @@ jobs:
             arch: arm_cortex-a7_neon-vfpv4
           - target: mediatek/filogic
             arch: aarch64_cortex-a53
-    runs-on: ubuntu-latest
+    # 26.04: the OpenWrt SDK refuses its non-GNU install
+    runs-on: ubuntu-24.04
     steps:
     - uses: actions/checkout@v7
 

.github/workflows/build-rpm-x86-64.yml

@@ -18,7 +18,8 @@ jobs:
     strategy:
       matrix:
         target:
-          - ubuntu-latest
+          # 26.04: rpm 6 runs %__gpg_sign_cmd differently, signing fails
+          - ubuntu-24.04
     runs-on: ${{ matrix.target }}
     steps:
     - uses: actions/checkout@v7