Export shadowhook_get_init_errno from the shared library

[dajiaohuang]

This PR fixes #120

Problem

shadowhook_get_init_errno is declared in the public native header and implemented by the library, but the shared-library version script does not export it. Native clients therefore cannot link this public API through libshadowhook.so.

Changes

• Add shadowhook_get_init_errno to the global export list.
• Reference the API from the existing systest library so its native link step guards the export.

Verification

• Ran a source consistency check that verifies the declaration, definition, single export-map entry, and systest link reference.
• Ran git diff --check.

The Android native build was not run locally because this Windows environment has no Android SDK, NDK, or repository-required CMake installation.

[caikelun]

Thanks. Please update your PR: keep only the changes to shadowhook/src/main/cpp/shadowhook.map.txt.

(I don't think it is necessary to specifically test the shadowhook_get_init_errno function in systest/src/main/cpp/systest.c; systest.c is intended for testing the hooking and interception of common system functions.)

[dajiaohuang]

Updated in 9cadf00: I removed the systest.c change, so the PR now changes only shadowhook/src/main/cpp/shadowhook.map.txt.

Validation:

• source consistency check confirmed one declaration, one definition, and one export-map entry for shadowhook_get_init_errno
• git diff --check upstream/dev...HEAD