I hate to sound dense, but what does this actually mean that I should do?No package 'claws-mail' found
Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.
Alternatively, you may set the environment variables CLAWS_MAIL_CFLAGS
and CLAWS_MAIL_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.
TIA