[build] install scripts/srt-ffplay in the bin directory

We don't need to use CMAKE_INSTALL_BINDIR which is not defined when
GNUInstallDirs is not used. Using "TYPE BIN" will have the same result
and will automatically pick the same as CMAKE_INSTALL_BINDIR.

https://cmake.org/cmake/help/latest/command/install.html#installing-files

CMakeLists.txt

@@ -1380,7 +1380,13 @@ if (ENABLE_UNITTESTS AND ENABLE_CXX11)
 endif()
 
 
-install(PROGRAMS scripts/srt-ffplay DESTINATION ${CMAKE_INSTALL_BINDIR})
+if(NOT NEED_DESTINATION)
+	install(PROGRAMS scripts/srt-ffplay TYPE BIN)
+elseif (DEFINED CMAKE_INSTALL_BINDIR)
+	install(PROGRAMS scripts/srt-ffplay DESTINATION ${CMAKE_INSTALL_BINDIR})
+else()
+	message(WARNING "No location to install scripts/srt-ffplay")
+endif()
 
 
 if (DEFINED SRT_EXTRA_APPS_INC)