Describe the bug

; should be escaped in CMake's add_compile_definitions where it is used in Conan. Compare:

add_compile_definitions("MYLIST=a;b;c")

generates -DMYLIST=a -Db -Dc!

add_compile_definitions("MYLIST=a\;b\;c")

generates -DMYLIST=a;b;c.

Relates to #15926, #14951.

How to reproduce it

E.g. use tools.build:defines=['MYLIST=a;b;c'], but this is not the only place in Conan where it is used.