external/gpgmepp: Deprecated std::shared_pointer::unique has been removed...

...from C++20, and is no longer provided at least by VS 2019 16.6.4 when using
--with-latest-c++

Change-Id: I1812b4c314febe134a299e42362ca50b495f08d9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/99081
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

external/gpgmepp/UnpackedTarball_gpgmepp.mk

@@ -28,5 +28,6 @@ $(eval $(call gb_UnpackedTarball_add_patches,gpgmepp, \
     $(if $(filter LINUX,$(OS)),external/gpgmepp/rpath.patch) \
     external/gpgmepp/gcc9.patch \
     external/gpgmepp/ubsan.patch \
+    external/gpgmepp/c++20.patch \
 ))
 # vim: set noet sw=4 ts=4:

external/gpgmepp/c++20.patch

@@ -0,0 +1,11 @@
+--- lang/cpp/src/keylistresult.cpp
++++ lang/cpp/src/keylistresult.cpp
+@@ -77,7 +77,7 @@
+ 
+ void GpgME::KeyListResult::detach()
+ {
+-    if (!d || d.unique()) {
++    if (!d || d.use_count() == 1) {
+         return;
+     }
+     d.reset(new Private(*d));