configure: error: Package requirements (openssl) were not met.
Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.
Alternatively you may set the OPENSSL_CFLAGS and OPENSSL_LIBS
environment variables to avoid the need to call pkg-config.
Libp11 is a library implementing a small layer on top of PKCS#11 API to make
using PKCS#11 implementations easier.
The official name for PKCS#11 is "RSA Security Inc. PKCS #11 Cryptographic
Token Interface (Cryptoki)".
Libp11 source code include the official header files (version 2.20) and thus
is "derived from the RSA Security Inc. PKCS #11 Cryptographic Token Interface
(Cryptoki)".