Problem: CACHELINE_SIZE conditions check string after numeric comparisons

When getconf returns "undefined" (e.g., on s390x under qemu-user), the
STREQUAL "undefined" check comes after EQUAL 0 and EQUAL -1. While this
works in current CMake versions, performing numeric comparisons on
non-numeric strings before string comparisons is fragile and could have
undefined behavior in some CMake versions.

Solution: reorder conditions to check strings before numeric comparisons

Move STREQUAL "undefined" before the EQUAL comparisons. This ensures
proper string matching is attempted before any numeric coercion, making
the code more robust and easier to understand.

Verified with qemu-user s390x emulation (CMake 3.22):
- getconf LEVEL1_DCACHE_LINESIZE returns "undefined"
- Both orderings work, but string-first is safer

Fixes #4834

Author: jiridanek

CMakeLists.txt

@@ -491,9 +491,9 @@ execute_process(
   OUTPUT_VARIABLE CACHELINE_SIZE
   ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
 if(CACHELINE_SIZE STREQUAL ""
+   OR CACHELINE_SIZE STREQUAL "undefined"
    OR CACHELINE_SIZE EQUAL 0
-   OR CACHELINE_SIZE EQUAL -1
-   OR CACHELINE_SIZE STREQUAL "undefined")
+   OR CACHELINE_SIZE EQUAL -1)
   set(ZMQ_CACHELINE_SIZE 64)
 else()
   set(ZMQ_CACHELINE_SIZE ${CACHELINE_SIZE})