get headless build to work again for Linux

This makes --disable-gui option build successfully again - which
means we again run on a headless server w/o any X11 or OpenGL libs.

Change-Id: I60019af571aecdac277adbe6d34d5fff065014f9
Reviewed-on: https://gerrit.libreoffice.org/50214
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

desktop/source/lib/init.cxx

@@ -2016,7 +2016,7 @@ static void doc_paintTile(LibreOfficeKitDocument* pThis,
         return;
     }
 
-#if defined(UNX) && !defined(MACOSX) && !defined(ENABLE_HEADLESS)
+#if defined(UNX) && !defined(MACOSX)
 
 #if defined(IOS)
     SystemGraphicsData aData;

desktop/unx/source/splashx.c

@@ -9,7 +9,7 @@
 
 #include "splashx.h"
 
-#ifdef ENABLE_QUICKSTART_LIBPNG
+#if defined(ENABLE_QUICKSTART_LIBPNG) && !defined(LIBO_HEADLESS)
 
 #include <X11/Xlib.h>
 #include <X11/Xatom.h>

framework/source/fwe/helper/titlehelper.cxx

@@ -562,8 +562,10 @@ void TitleHelper::impl_appendDebugVersion (OUStringBuffer& sTitle)
     OUString sVersion = ::utl::Bootstrap::getBuildIdData("development");
     sTitle.append(" [");
     sTitle.append(sVersion);
+#ifndef LIBO_HEADLESS
     if (OpenGLWrapper::isVCLOpenGLEnabled())
         sTitle.append("-GL");
+#endif
     sTitle.append("]");
 }
 #else