build: Try lua-5.3 when finding Lua

On FreeBSD, the executable is called 'lua53', but the .pc file has the
file name 'lua-5.3.pc'.
1 job for wip/lantw/build-try-lua-5.3 in 2 minutes and 52 seconds (queued for 9 seconds)
Status Job ID Name Coverage
  Test
passed #81757
build_stable

00:02:52