Make CPDB work with --enable-cpdb --disable-cups

The `PrinterInfoManager` implementation in
vcl/unx/generic/printer/printerinfomanager.cxx
takes care of actually using the `CUPSManager`
or the `CPDManager` for handling printers/printing.

Therefore, build that one also when `--disable-cups`
is used in addition to `--enable-cpdb`, and only make
the CUPS-specific bits depend on `ENABLE_CUPS`,
rather than building the dummy version of the
`PrinterInfoManager` implemented in
vcl/null/printerinfomanager.cxx.

This makes the CPDB printers show up in the print
dialog with WIP Gerrit change [1] in place in
addition.

[1] https://gerrit.libreoffice.org/c/core/+/169617/25

Change-Id: I5dddc72b8e679a84225f1dfb9c87d7562613a9f7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/172401
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Jenkins

vcl/Library_vcl.mk

@@ -634,6 +634,8 @@ $(eval $(call gb_Library_add_exception_objects,vcl,\
     $(if $(USE_HEADLESS_CODE), \
         $(if $(ENABLE_CUPS), \
             vcl/unx/generic/printer/cupsmgr \
+	) \
+	$(if $(filter TRUE,$(ENABLE_CPDB) $(ENABLE_CUPS)),\
             vcl/unx/generic/printer/printerinfomanager \
         , \
             vcl/null/printerinfomanager \

vcl/unx/generic/printer/printerinfomanager.cxx

@@ -18,12 +18,16 @@
  */
 
 #include <config_cpdb.h>
+#include <config_cups.h>
 
 #if ENABLE_CPDB
 #include <unx/cpdmgr.hxx>
 #endif
 
+#if ENABLE_CUPS
 #include <unx/cupsmgr.hxx>
+#endif
+
 #include <unx/gendata.hxx>
 #include <unx/helper.hxx>
 
@@ -89,8 +93,10 @@ PrinterInfoManager& PrinterInfoManager::get()
 #if ENABLE_CPDB
     pPIM = CPDManager::tryLoadCPD();
 #endif
+#if ENABLE_CUPS
     if (!pPIM)
         pPIM = CUPSManager::tryLoadCUPS();
+#endif
     if (!pPIM)
         pPIM = new PrinterInfoManager();
     pSalData->m_pPrinterInfoManager.reset(pPIM);