[CMake] How to avoid escaping $?

[Thomas Törnblom]

I have a need to add an argument like "-DImage$$= " to a compile 
command, i.e. define a macro Image$$ to just expand to a single space 
character.

I'm using Windows 10  and I configure my project to use Unix Makefiles 
for building. cmake appears to use "sh" (bash) to execute the build 
commands, and I have this in one of my cmake files:
---
     function(config_setting_shared_compiler_flags tgt)
         embedded_set_target_compile_flags(TARGET ${tgt} LANGUAGE C 
FLAGS ${COMMON_COMPILE_FLAGS} "-DImage$$= " "-DLoad$$LR$$= " 
"-D$$ZI$$Base=$$Base" "-D$$ZI$$Limit=$$Limit" "-D$$RO$$Base=$$Base" 
"-D$$RO$$Limit=$$Limit" "-D_DATA$$RW$$Base=_DATA$$Base" 
"-D_DATA$$RW$$Limit=_DATA$$Limit" "-D_DATA$$ZI$$Base=_DATA$$Base" 
"-D_DATA$$ZI$$Limit=_DATA$$Limit" "-D_STACK$$ZI$$Base=_STACK$$Base" 
"-D_STACK$$ZI$$Limit=_STACK$$Limit" )
     endfunction()
---

When doing a verbose build I see that the relevant part of the command 
lines expands to:
---
"-DImage\$\$= "
---
I.e. cmake has escaped the dollar signs with a \, which is what a normal 
unix shell needs, and this works fine on my system.

We've tried to build this project on a system with Windows 7, which has 
no working bash, and it uses cmd.exe to run the build lines. cmd.exe 
does not handle the \ escape the way bash does so the the build fails.

cmd.exe accepts the following syntax:
---
"-DImage$$= "
---

So no need to escape the dollar signs.

Is there a way to stop cmake from escaping dollar signs in this case?

/Thomas