ui/app: introduce DataDir for application-specific data files

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/app/datadir_android.go

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// +build android
+
+package app
+
+import "C"
+
+var dataDir func() (string, error)
+
+//export setDataDir
+func setDataDir(cdir *C.char) {
+	dir := C.GoString(cdir)
+	dataDir = func() (string, error) {
+		return dir, nil
+	}
+}
+