solver: if pinning is specified, it overrides preferred repos

add also a test case for this

src/solver.c

@@ -256,7 +256,7 @@ static void inherit_pinning(struct apk_solver_state *ss, struct apk_package *pkg
 	pkg->ss.pinning_allowed |= pinning;
 	pkg->ss.tag_ok |= !!(repos & repo_mask);
 	if (prefer) {
-		pkg->ss.pinning_preferred |= pinning;
+		pkg->ss.pinning_preferred = pinning;
 		pkg->ss.tag_preferred = !!(repos & apk_db_get_pinning_mask_repos(ss->db, pkg->ss.pinning_preferred));
 	}
 }

test/pinning-basic.repo

@@ -18,3 +18,9 @@ S:1
 I:1
 D:a>=2
 
+C:Q1eVpkasfqZAukArrYbg324xt4WUX=
+P:samever
+V:10
+S:1
+I:1
+

test/pinning-overlay1.repo

@@ -18,3 +18,9 @@ S:1
 I:1
 D:a>=3
 
+C:Q1eVpkasfqZAukArrYbg324xt4WUr=
+P:samever
+V:10
+S:1
+I:1
+

test/pinning13.test

+@ARGS
+--test-repo pinning-basic.repo
+--test-repo testing:pinning-overlay1.repo
+add samever@testing
+@EXPECT
+(1/1) Installing samever@testing (10)
+OK: 0 MiB in 0 packages