Fix g_stamp_svn error

"svn info" produces French string that are not properly parsed by quartus_generic.sh

tools/quartus/set_quartus

@@ -36,6 +36,10 @@ echo "  - Site setting: ${SITE-}"
 
 # Select tool version
 if [ "${SITE-}" = "USN" ]; then
+  # svn info produces French string that are not properly parsed by quartus_generic.sh
+  export LANG=C
+  export LC_MESSAGES=C
+
   if [ "${TOOLSET}" = "unb1" ]; then
     . ${RADIOHDL}/tools/quartus/quartus_version.sh 11.1sp2
   elif [ "${TOOLSET}" = "unb2" ]; then