CMake: Fix Interrogate macro not working on Windows

This was broken by 2d5bdb351557ed1ee51e4026aac26e251045c2a0,
which wrote -D flags as -D'symbol' -- this choked Windows,
so this commit turns it off in that case.

It's a shame there's no generator expression to escape quotes,
otherwise this hack wouldn't even be needed.

cmake/macros/Interrogate.cmake

@@ -210,7 +210,12 @@ function(interrogate_sources target output database language_flags)
   # in the same way that they are passed to the compiler so that Interrogate
   # will preprocess each file in the same way.
   set(_compile_defs "$<TARGET_PROPERTY:${target},COMPILE_DEFINITIONS>")
-  set(define_flags "$<$<BOOL:${_compile_defs}>:-D'$<JOIN:${_compile_defs},'\t-D'>'>")
+  if(NOT CMAKE_HOST_WIN32)
+    # Win32's command-line parser doesn't understand "'"
+    # that's fine, it also ignores '"'
+    set(_q "'")
+  endif()
+  set(define_flags "$<$<BOOL:${_compile_defs}>:-D${_q}$<JOIN:${_compile_defs},${_q}\t-D${_q}>${_q}>")
 
   # If this is a release build that has NDEBUG defined, we need that too:
   foreach(build_type ${CMAKE_CONFIGURATION_TYPES} ${CMAKE_BUILD_TYPE})