[components][lwp] Remove terminal/ from global CPPPATH

The terminal subsystem's own headers (terminal.h, tty_config.h, ...) are
resolved by the compiler's quoted-include directory lookup for sources
inside components/lwp/terminal; nothing else depends on the path.
Stop polluting the global CPPPATH with this internal directory,
following the convention discussed in #10980.

components/lwp/SConscript

@@ -45,10 +45,11 @@ if platform in platform_file.keys(): # support platforms
         CPPPATH += [cwd + '/arch/' + arch + '/' + cpu]
 
 # Terminal I/O Subsystem
+# terminal/*.c resolve their own headers via quoted-include directory lookup;
+# keep the internal path out of the global CPPPATH
 termios_path = ['./terminal/', './terminal/freebsd/']
 for item in termios_path:
     src += Glob(item + '*.c')
-CPPPATH += ['./terminal/']
 
 # Remove optional sources
 if not GetDepend(['LWP_USING_RUNTIME']):