devutils/set_quilt_vars.sh: Add refresh arg --strip-trailing-whitespace

Thanks for the suggestion in https://github.com/Eloston/ungoogled-chromium/pull/1011#issuecomment-618590125

devutils/set_quilt_vars.sh

@@ -18,7 +18,7 @@ export QUILT_PUSH_ARGS="--color=auto"
 export QUILT_DIFF_OPTS="--show-c-function"
 export QUILT_PATCH_OPTS="--unified --reject-format=unified"
 export QUILT_DIFF_ARGS="-p ab --no-timestamps --no-index --color=auto --sort"
-export QUILT_REFRESH_ARGS="-p ab --no-timestamps --no-index --sort"
+export QUILT_REFRESH_ARGS="-p ab --no-timestamps --no-index --sort --strip-trailing-whitespace"
 export QUILT_COLORS="diff_hdr=1;32:diff_add=1;34:diff_rem=1;31:diff_hunk=1;33:diff_ctx=35:diff_cctx=33"
 export QUILT_SERIES_ARGS="--color=auto"
 export QUILT_PATCHES_ARGS="--color=auto"