qga: vss-win32: Fix build failure

Hello,

These patches are to fix recent build failures of qemu-guest-agent for Windows when fsfreeze using VSS is enabled by:

  ./configure --cross-prefix=i686-w64-mingw32- --with-vss-sdk=yes

---
Tomoki Sekiyama (2):
Makefile: add qga-vss-dll-obj-y to nested variables
vss-win32: Fix build with mingw64-headers-3.1.0

 Makefile                  |    1 +
 qga/vss-win32/install.cpp |    3 +++
 2 files changed, 4 insertions(+)

Tomoki Sekiyama

The build rule for qga/vss-win32/qga-vss.dll is broken by commit ba1183da9a10b94611cad88c44a5c6df005f9b55, because it misses qga-vss-dll-obj-y in the list of nested variables.
This fixes build of qga-vss.dll by adding qga-vss-dll-obj-y to the list.

---
 Makefile |    1 +
 1 file changed, 1 insertion(+)

index ec74039..b6b09a9 100644
@@ -133,6 +133,7 @@ dummy := $(call unnest-vars,, \
                 stub-obj-y \
                 util-obj-y \
                 qga-obj-y \
+                qga-vss-dll-obj-y \
                 block-obj-y \
                 block-obj-m \
                 common-obj-y \

In mingw64-headers-3.1.0, definition of _com_issue_error() is added, which conflicts with definition in install.cpp. This adds version checking for mingw headers to disable the definition when the headers>=3.1 is used.

---
 qga/vss-win32/install.cpp |    3 +++
 1 file changed, 3 insertions(+)

index b791a6c..b0e4426 100644
@@ -75,10 +75,13 @@ static void errmsg_dialog(DWORD err, const char *text, const char *opt = "")
 
 #define chk(status) _chk(hr, status, "Failed to " #status, out)
 
+#if !defined(__MINGW64_VERSION_MAJOR) || !defined(__MINGW64_VERSION_MINOR) || \
+    __MINGW64_VERSION_MAJOR * 100 + __MINGW64_VERSION_MINOR < 301
 void __stdcall _com_issue_error(HRESULT hr)
 {
     errmsg(hr, "Unexpected error in COM");
 }
+#endif
 
 template<class T>
 HRESULT put_Value(ICatalogObject *pObj, LPCWSTR name, T val)