packaging: configure QEMU with -O2

Currently the the configure-hypervisor.sh doesn't set any optimization flag when
compiling QEMU >= 5.2.0 since the configure script will implicitly set -O2 on Ubuntu. But
on other environments, for example CentOS 7, it won't be set any optimization and this
results on the compiler warn:

  # warning _FORTIFY_SOURCE requires compiling with optimization (-O)

To avoid this inconsistent behavior across different build environments, let's explicitly
set the -O2 flag.

Reported-by: Eric Ernst <eric.g.ernst@gmail.com>
Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>

tools/packaging/scripts/configure-hypervisor.sh

@@ -474,6 +474,8 @@ generate_qemu_options() {
 	# On version 5.2.0 onward the Meson build system warns to not use -O3
 	if ! gt_eq "${qemu_version}" "5.2.0" ; then
 		_qemu_cflags+=" -O3"
+	else
+		_qemu_cflags+=" -O2"
 	fi
 
 	# Improve code quality by assuming identical semantics for interposed