make fatal error: openssl/sha.h: No such file or directory
probably you are missing the openssl header files. depending on your distribution this package might have a different name, mostly it's something like
openssl-devel. after you installed the openssl header files, the compiler should be able to find openssl/sha.h.
In Ubuntu/Debian the package is called
Turns out it was "libcurl4-openssl-dev". Not sure what libcurl has do do with SSL or SHA256, but it worked.
@tkbx `/usr/include/openssl/sha.h` is in `libssl-dev` in oldstable, stable and unstable.