Tests: Fix CMakeOnly.find_library test logic for libx32 case

Teach `test_find_library_subst` how to convert `libx32` to `lib`
so that the test case actually covers what we intend it to.

Tests/CMakeOnly/find_library/CMakeLists.txt

@@ -24,7 +24,7 @@ endmacro()
 macro(test_find_library_subst expected)
   get_filename_component(dir ${expected} PATH)
   get_filename_component(name ${expected} NAME)
-  string(REGEX REPLACE "lib/?[36X][24Y][Z]*" "lib" dir "${dir}")
+  string(REGEX REPLACE "lib/?[36Xx][24Y3][Z2]*" "lib" dir "${dir}")
   test_find_library(", searched as ${dir}" "${expected}"
     NAMES ${name}
     PATHS ${CMAKE_CURRENT_SOURCE_DIR}/${dir}