[atkmm] NMake Makefiles: Add option to use Meson-built libsigc++

[Chun-wei Fan <fanchunwei src gnome org>]

commit b6c762e56071249e43a0b678f9bc64bb279b2542
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Feb 7 19:07:54 2020 +0800

    NMake Makefiles: Add option to use Meson-built libsigc++
    
    This makes it easier for people to build and link against Meson-built
    libsigc++-3.x, by providing an NMake command line option.

 MSVC_NMake/config-msvc.mak | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/MSVC_NMake/config-msvc.mak b/MSVC_NMake/config-msvc.mak
index b2df058..2100c37 100644
--- a/MSVC_NMake/config-msvc.mak
+++ b/MSVC_NMake/config-msvc.mak
@@ -42,9 +42,14 @@ LIBATKMM_CFLAGS = /DATKMM_BUILD $(ATKMM_BASE_CFLAGS) $(ATKMM_EXTRA_INCLUDES)
 # We build atkmm-vc$(VSVER)0-$(ATKMM_MAJOR_VERSION)_$(ATKMM_MINOR_VERSION).dll or
 #          atkmm-vc$(VSVER)0-d-$(ATKMM_MAJOR_VERSION)_$(ATKMM_MINOR_VERSION).dll at least
 
+!ifdef USE_MESON_LIBS
+LIBSIGC_LIBNAME = sigc-$(LIBSIGC_MAJOR_VERSION).$(LIBSIGC_MINOR_VERSION)
+LIBSIGC_DLL = $(LIBSIGC_LIBNAME)-0.dll
+!else
 LIBSIGC_LIBNAME = sigc-vc$(VSVER)0$(DEBUG_SUFFIX)-$(LIBSIGC_MAJOR_VERSION)_$(LIBSIGC_MINOR_VERSION)
-
 LIBSIGC_DLL = $(LIBSIGC_LIBNAME).dll
+!endif
+
 LIBSIGC_LIB = $(LIBSIGC_LIBNAME).lib
 
 GLIBMM_LIBNAME = glibmm-vc$(VSVER)0$(DEBUG_SUFFIX)-$(GLIBMM_MAJOR_VERSION)_$(GLIBMM_MINOR_VERSION)