backend-rdp: fix unresolved symbols errors

The RDP backend uses functions defined by the Windows Portable Runtime
library (WinPR). The library's code is contained within FreeRDP
repository, but it is packaged as its own library (seperate pkg-config
file).

WinPR is added as a dependency to the RDP backend. The version 2.0 is
choosen as the version to on since the backend depends on FreeRDP 2.0.

Signed-off-by: Guillaume Champagne <champagne.guillaume.c@gmail.com>

libweston/backend-rdp/meson.build

@@ -9,6 +9,11 @@ if not dep_frdp.found()
 	error('RDP-backend requires freerdp2 which was not found. Or, you can use \'-Dbackend-rdp=false\'.')
 endif
 
+dep_wpr = dependency('winpr2', version: '>= 2.0.0', required: false)
+if not dep_wpr.found()
+	error('RDP-backend requires winpr2 which was not found. Or, you can use \'-Dbackend-rdp=false\'.')
+endif
+
 if cc.has_header('freerdp/version.h', dependencies: dep_frdp)
 	config_h.set('HAVE_FREERDP_VERSION_H', '1')
 endif
@@ -24,6 +29,7 @@ endif
 deps_rdp = [
 	dep_libweston_private,
 	dep_frdp,
+	dep_wpr,
 ]
 plugin_rdp = shared_library(
 	'rdp-backend',