Fix diff command to only set --strip-trailing-cr if available (#152)

contrib/tests/shpproj.sh

@@ -21,8 +21,19 @@ readonly SCRIPTDIR=$(dirname "$0")
 
 "${SHPDUMP:-$top_builddir/shpdump}" -precision 8 "test" > "test.out"
 
-
-if result=$(diff --strip-trailing-cr "$SCRIPTDIR/expect.out" "test.out"); then
+supports_strip_trailing_cr() {
+	diff --help 2>/dev/null | grep -q -- '--strip-trailing-cr'
+}
+
+run_diff() {
+	if supports_strip_trailing_cr; then
+		diff --strip-trailing-cr "$SCRIPTDIR/expect.out" "test.out"
+	else
+		diff "$SCRIPTDIR/expect.out" "test.out"
+	fi
+}
+
+if result=$(run_diff); then
 	echo "******* Test Succeeded *********"
 	exit 0
 else