Build Issue with ROOT 6.16.00 (OpenSSL)

Hi,

The build of ROOT 6.16.00 fails to build on Ubuntu 18.04 at the build step of OpenSSL:

...
[  0%] Performing build step for 'OPENSSL'                                                                                                                                  
CMake Error at /root/software/root/6.16.00/build/builtins/openssl/OPENSSL-prefix/src/OPENSSL-stamp/OPENSSL-build-RelWithDebInfo.cmake:16 (message):                           
Command failed: 2                   
                                                                                                                                                                                                                                                                                                                     
'make' '-j1' 'CC=/usr/bin/cc -fPIC '        
                                                                                                                                                                                                                                                                                                           
See also                                              
                                                                                                                                                                                                                                                                                                    
/root/software/root/6.16.00/build/builtins/openssl/OPENSSL-prefix/src/OPENSSL-stamp/OPENSSL-build-*.log             

                                                                                                                                                                                                                                                                                                                                                                                                            builtins/openssl/CMakeFiles/OPENSSL.dir/build.make:111: recipe for target 'builtins/openssl/OPENSSL-prefix/src/OPENSSL-stamp/OPENSSL-build' failed                          
make[2]: *** [builtins/openssl/OPENSSL-prefix/src/OPENSSL-stamp/OPENSSL-build] Error 1                                                                                      
CMakeFiles/Makefile2:895: recipe for target 'builtins/openssl/CMakeFiles/OPENSSL.dir/all' failed                                                                            
make[1]: *** [builtins/openssl/CMakeFiles/OPENSSL.dir/all] Error 2                                                                                                          
Makefile:151: recipe for target 'all' failed                                                                                                                                
make: *** [all] Error 2     

The end of builtins/openssl/OPENSSL-prefix/src/OPENSSL-stamp/OPENSSL-build-err.log

...
In file included from err_all.c:105:0:
../../include/openssl/cms.h:193:52: error: unknown type name 'ossl_ssize_t'; did you mean '__ssize_t'?
                               unsigned char *pass, ossl_ssize_t passlen);
                                                                  ^~~~~~~~~~~~
                                                                  __ssize_t
../../include/openssl/cms.h:233:37: error: unknown type name 'ossl_ssize_t'; did you mean '__ssize_t'?
                                     ossl_ssize_t passlen);
                                     ^~~~~~~~~~~~
                                     __ssize_t
../../include/openssl/cms.h:239:48: error: unknown type name 'ossl_ssize_t'; did you mean '__ssize_t'?
                                                ossl_ssize_t passlen,
                                                ^~~~~~~~~~~~
                                                __ssize_t
make[5]: *** [err_all.o] Error 1              
make[4]: *** [subdirs] Error 1                                                                                                                                              
make[3]: *** [build_crypto] Error 1

Any suggestions are appreciated.

Thanks


ROOT Version: 6.16.00
Platform: Ubuntu 18.04
Compiler: gcc 7.3.0


Removing the openssl build directory and rebuilding seems to have resolved the issue.