After 8046002, OracleUcrypto provider is added to OpenJDK without the Solaris headers it depends on. This is due to the assumption that the minimum Solaris version (S11) for JDK 9 should already have the necessary header files. However, the official Solaris build is still done using S10u6 devkit which doesn't have the necessary Ucrypto headers.
As a temporary work around, we added a custom libsoftcrypto.h. Once devkit is upgraded to a more recent version, this custom libsoftcrypto.h should be removed.