main/swig: specify python3 path otherwise check fails

main/swig/APKBUILD

@@ -1,7 +1,7 @@
 # Maintainer: Natanael Copa <ncopa@alpinelinux.org>
 pkgname=swig
 pkgver=3.0.12
-pkgrel=2
+pkgrel=3
 pkgdesc="A compiler that makes it easy to integrate C and C++ code with scripting languages"
 url="http://www.swig.org/"
 arch="all"
@@ -17,7 +17,8 @@ build() {
 	./configure \
 		--build=$CBUILD \
 		--host=$CHOST \
-		--prefix=/usr
+		--prefix=/usr \
+		--with-python3=/usr/bin/python
 	make
 }