Update build-scripts README.md with all available targets

Author: MBeijer

build-scripts/README.md

@@ -7,7 +7,7 @@ Helper script to build Emu68 with docker
 
 Syntax: build-with-docker [-t|v|c|b|h]
 Options:
--t		Sets which Emu68 target to build (raspi|raspi64|virt).
+-t		Sets which Emu68 target to build (raspi|raspi64|pbpro|rockpro64|virt).
 -v		Sets which Emu68 variant to build (none|pistorm).
 -c		Cleans build directory before building.
 -b		Builds example programs to run in Emu68.