Add --genCDeps for better integration with CMake (#20950)

* add gencdeps option

* add case statement

* Update compiler/main.nim

* Update compiler/main.nim

* Apply suggestions from code review

Fixes

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

compiler/options.nim

@@ -60,6 +60,7 @@ type                          # please make sure we have under 32 options
     optGenStaticLib,          # generate a static library
     optGenGuiApp,             # generate a GUI application
     optGenScript,             # generate a script file to compile the *.c files
+    optGenCDeps,              # generate a list of *.c files to be read by CMake
     optGenMapping,            # generate a mapping file
     optRun,                   # run the compiled project
     optUseNimcache,           # save artifacts (including binary) in $nimcache