meson: pick libfdt from common_ss when building target-specific files

Avoid having to list dependencies such as libfdt twice, both on common_ss
and specific_ss.  Instead, just take all the dependencies in common_ss
and allow the target-specific libqemu-*.fa library to use them.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/hw/ppc/meson.build b/hw/ppc/meson.build
index d096636..3ebbf32 100644
--- a/hw/ppc/meson.build
+++ b/hw/ppc/meson.build
@@ -3,9 +3,7 @@
   'ppc.c',
   'ppc_booke.c',
 ))
-ppc_ss.add(when: 'CONFIG_FDT_PPC', if_true: [files(
-  'fdt.c',
-), fdt])
+ppc_ss.add(when: 'CONFIG_FDT_PPC', if_true: files('fdt.c'))
 ppc_ss.add(when: 'CONFIG_FW_CFG_PPC', if_true: files('fw_cfg.c'))
 
 # IBM pSeries (sPAPR)