update c/buildah to v1.12.0

Also bump docker/docker.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/containers/common/pkg/unshare/unshare_gccgo.go

@@ -0,0 +1,25 @@
+// +build linux,cgo,gccgo
+
+package unshare
+
+// #cgo CFLAGS: -Wall -Wextra
+// extern void _containers_unshare(void);
+// void __attribute__((constructor)) init(void) {
+//   _containers_unshare();
+// }
+import "C"
+
+// This next bit is straight out of libcontainer.
+
+// AlwaysFalse is here to stay false
+// (and be exported so the compiler doesn't optimize out its reference)
+var AlwaysFalse bool
+
+func init() {
+	if AlwaysFalse {
+		// by referencing this C init() in a noop test, it will ensure the compiler
+		// links in the C function.
+		// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65134
+		C.init()
+	}
+}