add parameter buildconfig

Extend winpr and client/common to support a new option "/buildconfig".
When used build the following build specific information is print:
* cmake options
* cflags
* compiler
* target architecture
* cmake build type

.gitignore

@@ -21,6 +21,7 @@ LICENSE.txt
 *ConfigVersion.cmake
 include/freerdp/version.h
 include/freerdp/build-config.h
+buildflags.h
 
 *.a.objlist.cmake
 *.a.objlist