Ищ devel@:

Алексей, как я понимаю, в правиле опечатка, отсюда и получаем
CMake Error at libmariadb/cmake/ConnectorName.cmake:30 (ENDMACRO):
   Flow control statements are not properly nested.
Call Stack (most recent call first):
   libmariadb/CMakeLists.txt:423 (INCLUDE)

Исправляется так:
$ diff -u libmariadb/cmake/ConnectorName.cmake
libmariadb/cmake/ConnectorName.cmake.new
--- libmariadb/cmake/ConnectorName.cmake        2021-07-11 13:39:22.075170376
+0300
+++ libmariadb/cmake/ConnectorName.cmake.new    2021-07-11
13:39:16.929141979 +0300
@@ -22,7 +22,7 @@
      SET(MACHINE_NAME "x64")
    ELSE()
      SET(MACHINE_NAME "32")
-  END()
+  ENDIF()
  ENDIF()

mariadb-10.4.20-alt1 -> sisyphus:

 Sun Jul 11 2021 Alexey Shabalin <shaba@altlinux> 10.4.20-alt1
 - 10.4.20 (ALT #40403)
 - Fixes for the following security vulnerabilities:
   + CVE-2021-27928
   + CVE-2021-2166
   + CVE-2021-2154

Спасибо!