Ignore grep return code for MSI builds

So "grep -v" returns != 0, if your input or output file is empty.
which breaks the Jenkins build, because Jenkins runs scripts with
-xe per default.

The "strip comments" grep currently fails for the empty file
instsetoo_native/inc_openoffice/windows/msi_templates/components.txt

Change-Id: I53a477702dbcc3c00c4a23263c3b402cb936250a
(cherry picked from commit d526f5d7)
Reviewed-on: https://gerrit.libreoffice.org/19098Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>

instsetoo_native/CustomTarget_install.mk

@@ -65,7 +65,7 @@ define instsetoo_native_msitemplates
 TEMPLATE_DIR=$(dir $@)msi_templates \
 && rm -rf $${TEMPLATE_DIR} \
 && mkdir -p $${TEMPLATE_DIR}/Binary \
-&& for I in $(SRCDIR)/instsetoo_native/inc_$(1)/windows/msi_templates/*.* ; do $(GREP) -v '^#' "$$I" > $${TEMPLATE_DIR}/`basename $$I` ; done \
+&& for I in $(SRCDIR)/instsetoo_native/inc_$(1)/windows/msi_templates/*.* ; do $(GREP) -v '^#' "$$I" > $${TEMPLATE_DIR}/`basename $$I` || true ; done \
 && $(GNUCOPY) $(SRCDIR)/instsetoo_native/inc_common/windows/msi_templates/Binary/*.* $${TEMPLATE_DIR}/Binary
 endef
 else