[scripts] Add script to print clang prebuilts version

Bug: http://b/187231324

This script parses soong/cc/config/global.go to return clang prebuilts
version.  (It may get the version from a json config file in the
future.)

Currently it's used in development/scripts/symbol.py and is the
recommended way to get clang prebuilts version number in the future.

Test: get_clang_version_test.py
Change-Id: Id92a74fd523a5270999bb4d6454525bf2f2f0c04

scripts/Android.bp

@@ -265,3 +265,19 @@ python_binary_host {
         "linker_config_proto",
     ],
 }
+
+python_binary_host {
+    name: "get_clang_version",
+    main: "get_clang_version.py",
+    srcs: [
+        "get_clang_version.py",
+    ],
+    version: {
+        py2: {
+            enabled: false,
+        },
+        py3: {
+            enabled: true,
+        },
+    },
+}