Don't override PREFIX target property (#340)

PREFIX is by default "lib", which most of the libraries use.
this changes makes the library files libftxui-foo.a
as ArthurSonzogni/FTXUI#140 intended originally

CHANGELOG.md

@@ -4,8 +4,12 @@ Changelog
 current (development) 
 ---------------------
 
-#### DOM:
-- The `inverted` decorator now toggle in the inverted attribute.
+### Build
+- **breaking**: The library prefix is now back to "lib" (the default). This
+    means non-cmake users should not link against "libftxui-dom" for instance.
+
+### DOM:
+- **breaking**: The `inverted` decorator now toggle in the inverted attribute.
 - Add `gauge` for the 4 directions. Expose the following API:
 ```cpp
 Element gauge(float ratio);
@@ -20,7 +24,7 @@ Element gaugeDirection(float ratio, GaugeDirection);
 - Fix the `Table` rendering function, to allow automerging characters.
 - Bugfix: The `vscroll_indicator` now computes its offset and size correctly.
 
-#### Component
+### Component
 - Support SIGTSTP. (ctrl+z).
 - Support task posting. `ScreenInteractive::Post(Task)`.
 

cmake/ftxui_set_options.cmake

@@ -1,5 +1,5 @@
 function(ftxui_set_options library)
-  set_target_properties(${library} PROPERTIES PREFIX "ftxui-")
+  set_target_properties(${library} PROPERTIES OUTPUT_NAME "ftxui-${library}")
 
 
   target_include_directories(${library}