CPack/RPM: Add zstd compression support

Fixes: #26088

Help/cpack_gen/rpm.rst

@@ -246,9 +246,8 @@ List of CPack RPM generator specific variables:
  :Default: (system default)
 
  May be used to override RPM compression type to be used to build the
- RPM. For example some Linux distribution now default to ``lzma`` or ``xz``
+ RPM. For example some Linux distributions default to ``xz`` or ``zstd``.
- compression whereas older cannot use such RPM. Using this one can enforce
+ Using this, one can specify a specific compression type to be used.
- compression type to be used.
 
  Possible values are:
 
@@ -264,6 +263,11 @@ List of CPack RPM generator specific variables:
   ``gzip``
     GNU Gzip compression
 
+  ``zstd``
+    .. versionadded:: 3.31
+
+    Zstandard compression
+
 .. variable:: CPACK_RPM_PACKAGE_AUTOREQ
               CPACK_RPM_<component>_PACKAGE_AUTOREQ
 

Help/release/dev/cpack-rpm-zstd.rst

@@ -0,0 +1,5 @@
+cpack-rpm-zstd
+--------------
+
+* The :cpack_gen:`CPack RPM Generator` gained support for ``zstd`` as a
+  :variable:`CPACK_RPM_COMPRESSION_TYPE` value.

Modules/Internal/CPack/CPackRPM.cmake

@@ -1049,6 +1049,12 @@ function(cpack_rpm_generate_package)
       set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w9.bzdio")
     elseif(CPACK_RPM_COMPRESSION_TYPE STREQUAL "gzip")
       set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w9.gzdio")
+    elseif(CPACK_RPM_COMPRESSION_TYPE STREQUAL "zstd")
+      if(CPACK_THREADS GREATER "0")
+        set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w19T${CPACK_THREADS}.zstdio")
+      else()
+        set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w19T0.zstdio")
+      endif()
     else()
       message(FATAL_ERROR "Specified CPACK_RPM_COMPRESSION_TYPE value is not supported: ${CPACK_RPM_COMPRESSION_TYPE}")
     endif()