the svn fallback code added in r20322 is evaluated with each make invocation and produces a lot of spurious "svn: broken pipe" error - replace it with a more efficient version

SVN-Revision: 20377

include/download.mk

@@ -63,12 +63,6 @@ define DownloadMethod/cvs
 	)
 endef
 
-SVN_VERSION=$(shell svn --version | head -1 | awk '{ print $3 }' | cut -d. -f2)
-ifeq ($(SVN_VERSION),5)
-else
-SVN_OPTS:=--trust-server-cert
-endif
-
 define DownloadMethod/svn
 	$(call wrap_mirror, \
 		echo "Checking out files from the svn repository..."; \
@@ -76,7 +70,9 @@ define DownloadMethod/svn
 		cd $(TMP_DIR)/dl && \
 		rm -rf $(SUBDIR) && \
 		[ \! -d $(SUBDIR) ] && \
-		svn export --non-interactive $(SVN_OPTS) -r$(VERSION) $(URL) $(SUBDIR) && \
+		( svn help export | grep -q trust-server-cert && \
+		svn export --non-interactive --trust-server-cert -r$(VERSION) $(URL) $(SUBDIR) || \
+		svn export --non-interactive -r$(VERSION) $(URL) $(SUBDIR) ) && \
 		echo "Packing checkout..." && \
 		$(call dl_pack,$(TMP_DIR)/dl/$(FILE),$(SUBDIR)) && \
 		mv $(TMP_DIR)/dl/$(FILE) $(DL_DIR)/ && \