meson: Optimize summary_info about directories

Clear summary_info first, otherwise there will be redundant output
about build environment.

Signed-off-by: Bin Guo <guobin@linux.alibaba.com>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20251219230456.37178-1-guobin@linux.alibaba.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

meson.build

@@ -4650,6 +4650,7 @@ summary_info += {'Download dependencies': get_option('wrap_mode') != 'nodownload
 summary(summary_info, bool_yn: true, section: 'Build environment')
 
 # Directories
+summary_info = {}
 summary_info += {'Install prefix':    get_option('prefix')}
 summary_info += {'BIOS directory':    qemu_datadir}
 pathsep = host_os == 'windows' ? ';' : ':'