Pass $(MAKE) into external/gpgmepp

...similar to e8e5bd65 "Pass $(MAKE) into
external/libassuan"

Change-Id: Icb90eb0831e74270a2600ab8ea9a6b0ac88a7e5f
Reviewed-on: https://gerrit.libreoffice.org/45345Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
(cherry picked from commit e75c983a)
Reviewed-on: https://gerrit.libreoffice.org/45374Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

external/gpgmepp/ExternalProject_gpgmepp.mk

@@ -38,6 +38,7 @@ $(call gb_ExternalProject_get_state_target,gpgmepp,build):
 				$(if $(ENABLE_DEBUG),$(gb_DEBUG_CFLAGS)) \
 				$(if $(filter $(true),$(gb_SYMBOL)),$(gb_DEBUGINFO_FLAGS))' \
 		   --host=$(if $(filter INTEL,$(CPUNAME)),i686-mingw32,x86_64-w64-mingw32) \
+		   MAKE=$(MAKE) \
 	  && $(MAKE) \
 	)
 else