[evolution] Include also CFLAGS in gtkdoc-scangobj command line

[Milan Crha <mcrha src gnome org>]

commit 540d239705f5fa5a9064968d478408703af2aa01
Author: Milan Crha <mcrha redhat com>
Date:   Mon Aug 5 12:55:23 2019 +0200

    Include also CFLAGS in gtkdoc-scangobj command line
    
    The LDFLAGS could imply certain compile options being used (like -fPIC),
    but these CFLAGS were not passed to gtkdoc-scangobj, thus the compilation
    could fail.
    
    Related to https://gitlab.gnome.org/GNOME/evolution-data-server/merge_requests/28

 cmake/modules/GtkDoc.cmake | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/cmake/modules/GtkDoc.cmake b/cmake/modules/GtkDoc.cmake
index 0ba1a7a78a..2dfc4d6910 100644
--- a/cmake/modules/GtkDoc.cmake
+++ b/cmake/modules/GtkDoc.cmake
@@ -98,6 +98,7 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
 
        # Add it as the last, thus in-tree headers have precedence
        list(APPEND _scangobj_cflags_list -I${INCLUDE_INSTALL_DIR})
+       list(APPEND _scangobj_cflags_list ${CMAKE_C_FLAGS})
 
        if(_scangobj_deps)
                list(REMOVE_DUPLICATES _scangobj_deps)