Fix PAX build failure on GCC 8.x (Rocky Linux 8)

1. Remove explicit -Werror=pessimizing-move flag from CMakeLists.txt.
   This flag was added in commit e7e07c2 to catch pessimizing-move
   warnings on higher GCC versions, but it breaks compilation on GCC 8.x
   where this warning option does not exist. The fix is safe because
   GCC 9+ enables -Wpessimizing-move by default and the existing -Werror
   flag already converts all warnings to errors.

2. Fix fast_io.cc compatibility issues:
   - Add missing <unistd.h> include for pread()
   - Define uring_likely macro fallback for older liburing versions

See: Issue#1441 <https://github.com/apache/cloudberry/issues/1441\>

Author: tuhaihe

contrib/pax_storage/CMakeLists.txt

@@ -21,7 +21,10 @@ set(CMAKE_CXX_STANDARD 17)
 set(TOP_DIR ${PROJECT_SOURCE_DIR}/../..)
 set(CBDB_INCLUDE_DIR ${TOP_DIR}/src/include)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Werror -Werror=pessimizing-move  -Wno-unused-function -Wno-error=ignored-qualifiers -Wno-error=array-bounds  -Wuninitialized -Winit-self -Wstrict-aliasing -Wno-missing-field-initializers -Wno-unused-parameter -Wno-clobbered -Wno-sized-deallocation -g")
+# Base CXX flags
+# Note: -Wpessimizing-move is enabled by default in GCC 9+ and will be caught by -Werror
+# No need to explicitly add -Werror=pessimizing-move (which breaks GCC 8.x compatibility)
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Werror -Wno-unused-function -Wno-error=ignored-qualifiers -Wno-error=array-bounds -Wuninitialized -Winit-self -Wstrict-aliasing -Wno-missing-field-initializers -Wno-unused-parameter -Wno-clobbered -Wno-sized-deallocation -g")
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wno-unused-parameter -Wno-parameter-name")
 
 option(USE_MANIFEST_API "Use manifest API" OFF)

contrib/pax_storage/src/cpp/comm/fast_io.cc

@@ -27,6 +27,13 @@
 
 #include "fast_io.h"
 
+#include <unistd.h>  // for pread
+
+// uring_likely may not be defined in older liburing versions
+#ifndef uring_likely
+#define uring_likely(x) __builtin_expect(!!(x), 1)
+#endif
+
 namespace pax
 {