[gimp] app: GimpBacktrace Windows backend only available with Dr. Mingw.

[Jehan <jehanp src gnome org>]

commit 644234e99d18f9608e44c9a6338c73f3e4872168
Author: Jehan <jehan girinstud io>
Date:   Wed Sep 5 15:11:41 2018 +0200

    app: GimpBacktrace Windows backend only available with Dr. Mingw.
    
    (cherry picked from commit e7dde73f84925545c326f111913fa6b72c1a0825)

 app/core/gimpbacktrace-backend.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/app/core/gimpbacktrace-backend.h b/app/core/gimpbacktrace-backend.h
index 4bfb1c9434..837d26547a 100644
--- a/app/core/gimpbacktrace-backend.h
+++ b/app/core/gimpbacktrace-backend.h
@@ -24,7 +24,7 @@
 
 #ifdef __gnu_linux__
 # define GIMP_BACKTRACE_BACKEND_LINUX
-#elif defined (G_OS_WIN32) && defined (ARCH_X86)
+#elif defined (G_OS_WIN32) && defined (ARCH_X86) && defined (HAVE_EXCHNDL)
 # define GIMP_BACKTRACE_BACKEND_WINDOWS
 #else
 # define GIMP_BACKTRACE_BACKEND_NONE