Skip reading VNDK libs for product if not available

If a device do not define "ro.product.vndk.version", we don't need to
initialize the VNDK libraries for them. In that case, return emtpy
string.

Bug: 151992099
Test: atest libnativeloader_test
Change-Id: Ic4d5e0e1162d367e919b5381e3a6c7d048a5e103
1 file changed