meson: subprojects: replace submodules with wrap files

Compared to submodules, .wrap files have several advantages:

* option parsing and downloading is delegated to meson

* the commit is stored in a text file instead of a magic entry in the
  git tree object

* we could stop shipping external dependencies that are only used as a
  fallback, but not break compilation on platforms that lack them.
  For example it may make sense to download dtc at build time, controlled
  by --enable-download, even when building from a tarball.  Right now,
  this patch does the opposite: make-release treats dtc like libvfio-user
  (which is not stable API and therefore hasn't found its way into any
  distros) and keycodemap (which is a copylib, for better or worse).

dependency() can fall back to a wrap automatically.  However, this
is only possible for libraries that come with a .pc file, and this
is not very common for libfdt even though the upstream project in
principle provides it; it also removes the control that we provide with
--enable-fdt={system,internal}.  Therefore, the logic to pick system
vs. internal libfdt is left untouched.

--enable-fdt=git is removed; it was already a synonym for
--enable-fdt=internal.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 1 insertions, 14 deletions

diff --git a/meson.build b/meson.build
index f8af4b02e4..74fb147fde 100644
--- a/meson.build
+++ b/meson.build
@@ -3031,14 +3031,7 @@ endif
 
 libvfio_user_dep = not_found
 if have_system and vfio_user_server_allowed
-  have_internal = fs.exists(meson.current_source_dir() / 'subprojects/libvfio-user/meson.build')
-
-  if not have_internal
-    error('libvfio-user source not found - please pull git submodule')
-  endif
-
-  libvfio_user_proj = subproject('libvfio-user')
-
+  libvfio_user_proj = subproject('libvfio-user', required: true)
   libvfio_user_dep = libvfio_user_proj.get_variable('libvfio_user_dep')
 endif
 
@@ -3066,12 +3059,6 @@ if fdt_required.length() > 0 or fdt_opt == 'enabled'
   endif
   if not fdt.found()
     assert(fdt_opt == 'internal')
-    have_internal = fs.exists(meson.current_source_dir() / 'subprojects/dtc/meson.build')
-
-    if not have_internal
-      error('libfdt source not found - please pull git submodule')
-    endif
-
     libfdt_proj = subproject('dtc', required: true,
                              default_options: ['tools=false',  'yaml=disabled',
                                                'python=disabled', 'default_library=static'])