Fix portability for expr(1) usage

"match" operand for expr(1) is GNU extension.
Change to use the standard way to match regex with expr(1).

configure

@@ -576,7 +576,7 @@ if [ -x "./qcextra" ]; then
 	./qcextra
 fi
 # run tqmake
-if expr match "$DEB_BUILD_OPTIONS" ".*nostrip"; then
+if expr "$DEB_BUILD_OPTIONS" : ".*nostrip"; then
 	$qm QMAKE_STRIP=true qca-tls.pro
 else
 	$qm qca-tls.pro