Fix: Python build dependencies installation

Improve wheel and cython dependency management in gpMgmt/bin/Makefile
to handle Ubuntu 24.04's PEP 668 restrictions while maintaining
compatibility with Rocky Linux and older Ubuntu versions.

Changes:
- Split wheel and cython dependency checks into separate commands
- Add fallback to --break-system-packages flag for Ubuntu 24.04+
- Only install dependencies if not already present in the system
- Maintain backward compatibility with existing build environments

This resolves build failures on Ubuntu 24.04 where pip install --user
is restricted by default, while preserving the existing behavior on
Rocky Linux 8/9 and Ubuntu 20.04/22.04 systems.

Author: tuhaihe

gpMgmt/bin/Makefile

@@ -111,8 +111,19 @@ download-python-deps:
 	else \
 		echo "PyGreSQL-$(PYGRESQL_VERSION).tar.gz already exists, skipping download"; \
 	fi
-	# Install wheel and cython for PyYAML building
-	pip3 install --user wheel "cython<3.0.0"
+	# Install wheel and cython for PyYAML building (only if not exists)
+	@if python3 -c "import wheel" >/dev/null 2>&1; then \
+		echo "wheel already exists, skipping installation"; \
+	else \
+		echo "Installing wheel..."; \
+		pip3 install --user wheel 2>/dev/null || pip3 install --user --break-system-packages wheel; \
+	fi
+	@if python3 -c "import cython" >/dev/null 2>&1; then \
+		echo "cython already exists, skipping installation"; \
+	else \
+		echo "Installing cython..."; \
+		pip3 install --user "cython<3.0.0" 2>/dev/null || pip3 install --user --break-system-packages "cython<3.0.0"; \
+	fi
 
 #
 # PyGreSQL