| DEFINE_SYMBOL | |
| ------------- | |
| Define a symbol when compiling this target's sources. | |
| DEFINE_SYMBOL sets the name of the preprocessor symbol defined when | |
| compiling sources in a shared library. If not set here then it is set | |
| to target_EXPORTS by default (with some substitutions if the target is | |
| not a valid C identifier). This is useful for headers to know whether | |
| they are being included from inside their library or outside to | |
| properly setup dllexport/dllimport decorations. |