meson: build contrib/ executables after generated headers

This will be needed as soon as config-poison.h moves from configure to
a meson custom_target (which is built at "ninja" time).

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

contrib/elf2dmp/meson.build

 if curl.found()
-  executable('elf2dmp', files('main.c', 'addrspace.c', 'download.c', 'pdb.c', 'qemu_elf.c'),
+  executable('elf2dmp', files('main.c', 'addrspace.c', 'download.c', 'pdb.c', 'qemu_elf.c'), genh,
              dependencies: [glib, curl],
              install: true)
 endif

contrib/ivshmem-client/meson.build

-executable('ivshmem-client', files('ivshmem-client.c', 'main.c'),
+executable('ivshmem-client', files('ivshmem-client.c', 'main.c'), genh,
            dependencies: glib,
            build_by_default: targetos == 'linux',
            install: false)

contrib/ivshmem-server/meson.build

-executable('ivshmem-server', files('ivshmem-server.c', 'main.c'),
+executable('ivshmem-server', files('ivshmem-server.c', 'main.c'), genh,
            dependencies: [qemuutil, rt],
            build_by_default: targetos == 'linux',
            install: false)

contrib/rdmacm-mux/meson.build

@@ -2,7 +2,7 @@ if 'CONFIG_PVRDMA' in config_host
   # if not found, CONFIG_PVRDMA should not be set
   # FIXME: broken on big endian architectures
   libumad = cc.find_library('ibumad', required: true)
-  executable('rdmacm-mux', files('main.c'),
+  executable('rdmacm-mux', files('main.c'), genh,
              dependencies: [glib, libumad],
              build_by_default: false,
              install: false)