Do not let doxygen build man pages on Windows

This fixes an issue on gitlab CI not been able to create man page
output dir. Also man pages does not make sense on Windows.

Doxyfile.in

@@ -127,7 +127,7 @@ RTF_EXTENSIONS_FILE    =
 #---------------------------------------------------------------------------
 # configuration options related to the man page output
 #---------------------------------------------------------------------------
-GENERATE_MAN           = YES
+GENERATE_MAN           = @DBUS_GENERATE_MAN@
 MAN_OUTPUT             = man
 MAN_EXTENSION          = .3dbus
 MAN_LINKS              = YES

configure.ac

@@ -1269,6 +1269,13 @@ if test x$enable_doxygen_docs = xyes; then
     fi
 fi
 
+if test x$dbus_win = xno; then
+    DBUS_GENERATE_MAN=YES
+else
+    DBUS_GENERATE_MAN=NO
+fi
+AC_SUBST([DBUS_GENERATE_MAN])
+
 AM_CONDITIONAL(DBUS_DOXYGEN_DOCS_ENABLED, test x$enable_doxygen_docs = xyes)
 AC_MSG_RESULT($enable_doxygen_docs)
 

doc/CMakeLists.txt

@@ -12,6 +12,11 @@ endif()
 
 if(DBUS_ENABLE_DOXYGEN_DOCS)
     set(top_srcdir ${CMAKE_SOURCE_DIR})
+    if(WIN32)
+        set(DBUS_GENERATE_MAN NO)
+    else()
+        set(DBUS_GENERATE_MAN YES)
+    endif()
     configure_file(../Doxyfile.in ${CMAKE_BINARY_DIR}/Doxyfile )
     add_custom_command(
         OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/api/html/index.html