Building with vboot fails in a confusing way when pkg-config isn't installed
vboot uses pkg-config to find the right compiler options to link in libssl into futility (the userland tool for key management). With that not installed, the build will go through until the linker step fails because openssl symbols are missing.
Provide better output for
- pkg-config missing
- pkg-config installed but libssl not found by it (not sure what that looks like today)