Unneeded escape characters in cmake/generic_board.cmake

[markhermeling]

When using the pico-sdk in my own project, I received error messages saying
Using board configuration from /pico-sdk/src/boards/include/boards/pico_w.h
CMake Error at /pico-sdk/cmake/generic_board.cmake:22 (if):
Syntax error in cmake code at
/pico-sdk/cmake/generic_board.cmake:22
when parsing string
^[ \t]//[ \t]pico_cmake_set[ \t]([a-zA-Z_][a-zA-Z0-9_])[ \t]=[ \t](.*)
Invalid escape sequence ]
Call Stack (most recent call first):
/pico-sdk/cmake/pico_pre_load_platform.cmake:70 (include)
/pico-sdk/pico_sdk_init.cmake:87 (include)
pico_sdk_import.cmake:73 (include)
CMakeLists.txt:5 (include)

there are a couple of instances of ] in that cmake file that should be ]. All works correctly if I change them.

[will-v-pi]

Yes, this error only occurs when policy CMP0053 is set to OLD, but the pico-sdk will set this to NEW as the cmake_minimum_required is 3.13 which is >3.1

But you are correct that those escape sequences aren't necessary, so we should remove them - could you reopen your PR and we can merge it?

[markhermeling]

Created a new PR (I deleted the previous branch :).

[kilograham]

merged into develop