[evolution-data-server] M!28 - Include LDFLAGS in gtkdoc-scangobj command line

[Milan Crha <mcrha src gnome org>]

commit 925070132ca90787ccfe9a993c3eb7e0feb74fa7
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Mon Jul 22 16:06:21 2019 +0800

    M!28 - Include LDFLAGS in gtkdoc-scangobj command line
    
    When a library provides no way to find linker flags for linking with it,
    the build system usually depends on the user to necessary put -L flags
    in LDFLAGS environment variable in order to find it. However, GtkDoc
    module constructs the command line by itself, and it forgets to add
    LDFLAGS to the command line of gtkdoc-scangobj.
    
    It is especially important to include LDFLAGS on non-GNU systems. For
    example, FreeBSD libc doesn't include a gettext implementation. GLib
    requires gettext, and it pulls in an external gettext runtime for it.
    However, gettext-runtime doesn't include a .pc file, so LDFLAGS is
    required if gettext-runtime isn't installed in the same prefix as GLib.
    Failing to include LDFLAGS in --ldflags passed to gtkdoc-scangobj can
    result in a linking error because -lintl cannot be found.
    
    In evolution-data-server we are lucky most of the time because it
    depends on a lot of external libraries. These external libraries are
    likely to be installed in the same prefix as gettext-runtime, so not
    using LDFLAGS doesn't cause linking failure because required flags are
    already pulled in by other libraries. In fact, this problem was found
    when building libical, which uses a similar GtkDoc.cmake file.
    
    In addition to the change to include LDFLAGS, this commit also changes
    the following things:
    
     - Instead of constructing _scangobj_ldflags in reverse order, do it in
       normal order. Appending is easier to understand than prepending, and
       the linker also interprets -L and -l flags in normal order.
    
     - Move -L${LIB_INSTALL_DIR} to the bottom. This is what the comment
       says, and it is expected to work because we no longer constructs
       _scangobj_ldflags in reverse order.
    
    Closes https://gitlab.gnome.org/GNOME/evolution-data-server/merge_requests/28

 cmake/modules/GtkDoc.cmake | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/cmake/modules/GtkDoc.cmake b/cmake/modules/GtkDoc.cmake
index cc6cc007a..0ba1a7a78 100644
--- a/cmake/modules/GtkDoc.cmake
+++ b/cmake/modules/GtkDoc.cmake
@@ -96,9 +96,8 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
                list(APPEND _scangobj_deps ${opt})
        endforeach(opt)
 
-       # Add them as the last, thus in-tree headers/libs have precedence
+       # Add it as the last, thus in-tree headers have precedence
        list(APPEND _scangobj_cflags_list -I${INCLUDE_INSTALL_DIR})
-       list(APPEND _scangobj_ldflags -L${LIB_INSTALL_DIR})
 
        if(_scangobj_deps)
                list(REMOVE_DUPLICATES _scangobj_deps)
@@ -122,7 +121,7 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
                                if(NOT _output_name)
                                        set(_output_name ${opt})
                                endif(NOT _output_name)
-                               set(_scangobj_ldflags "-L$<TARGET_FILE_DIR:${opt}> -l${_output_name} 
${_scangobj_ldflags}")
+                               set(_scangobj_ldflags "${_scangobj_ldflags} -L$<TARGET_FILE_DIR:${opt}> 
-l${_output_name}")
 
                                if(_target_type STREQUAL "SHARED_LIBRARY" OR (_target_type STREQUAL 
"MODULE_LIBRARY"))
                                        set(_scangobj_ld_lib_dirs 
"${_scangobj_ld_lib_dirs}:$<TARGET_FILE_DIR:${opt}>")
@@ -133,12 +132,18 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
                endif(TARGET ${opt})
        endforeach(opt)
 
+       # Add extra flags from LDFLAGS environment variable
+       set(_scangobj_ldflags "${_scangobj_ldflags} ${CMAKE_SHARED_LINKER_FLAGS}")
+
        foreach(opt IN LISTS _scangobj_deps)
                if(NOT TARGET ${opt})
                        set(_scangobj_ldflags "${_scangobj_ldflags} ${opt}")
                endif(NOT TARGET ${opt})
        endforeach(opt)
 
+       # Add it as the last, thus in-tree libs have precedence
+       set(_scangobj_ldflags "${_scangobj_ldflags} -L${LIB_INSTALL_DIR}")
+
        set(_scangobj_prefix ${CMAKE_COMMAND} -E env 
LD_LIBRARY_PATH="${_scangobj_ld_lib_dirs}:${LIB_INSTALL_DIR}:$ENV{LD_LIBRARY_PATH}")
 
        if(NOT (_scangobj_cflags STREQUAL ""))