[AIX] Build failure after 11u backport of JDK-8247753

This is a JDK 11 specific bug as for later JDKs the code performing those checks is Java code. The JDK 11u backport in 11.0.12 introduced strcasestr function for case insensitive comparison. This breaks the AIX build with:

ld: 0711-317 ERROR: Undefined symbol: .strcasestr

Note that strcasestr is a GNU specific extension not available on AIX.