Fix build failures.

* Skip el8 target to avoid the following error.
  "error: one or more PCH files were found, but they were invalid".
* Set %_without_hardening_test macro to avoid checksec error on f30.

ruby.yaml

@@ -19,9 +19,9 @@ data:
     dependencies:
         - buildrequires:
             # platform: [] is recommended.
-            platform: []
+            platform: [-el8]
           requires:
-            platform: []
+            platform: [-el8]
     components:
         # SRPMs
         rpms:
@@ -66,6 +66,8 @@ data:
             macros: |
                 # To disable tests in several packages.
                 %_without_tests 1
+                # To avoid the error by rpms/ruby `checksec --file` on f30.
+                %_without_hardening_test 1
     api:
         # RPMs
         # From *.spec %package