Add config for portable build

Generate the java-21-openjdk portable from the c10s sources into the
a10s-portable branch: RHEL has not shipped the 21.0.12.1.1-2 update to
UBI 8 yet, so the portable at portablerelease 2 cannot be built from c8.
The portable specfile is identical in c8s, c9s and c10s.

Only %undefine pkgos is needed now; the riscv64 bits the old
config-portable-riscv64.yaml carried (debug_package, ARCH_DATA_MODEL,
ExclusiveArch, the RPM 4.19 %files fix) are all upstream.

config-portable.yaml

@@ -0,0 +1,29 @@
+parameters:
+  custom_target_branch: "a10s-portable"
+  pre_clean: true
+
+actions:
+  - run_script:
+      - script: "replace_spec.sh"
+        cwd: "rpms"
+
+  - replace:
+      - target: "spec"
+        find: |
+              %if 0%{?centos} != 0 && 0%{?centos} != 0%{centos_buildos}
+              %global pkgos rhel%{?centos}
+              %endif
+        replace: |
+              %if 0%{?centos} != 0 && 0%{?centos} != 0%{centos_buildos}
+              %global pkgos rhel%{?centos}
+              %endif
+              %if 0%{?almalinux}
+              %undefine pkgos
+              %endif
+        count: 1
+
+  - changelog_entry:
+      - name: "Eduard Abdullin"
+        email: "eabdullin@almalinux.org"
+        line:
+          - "Portable build"

scripts/replace_spec.sh

@@ -0,0 +1,2 @@
+rm java-21-openjdk.spec
+ln -s java-21-openjdk-portable.specfile java-21-openjdk.spec