Upgrade arm-none-eabi compiler

It was 5 years out of date and didn't fully support C++20.

In doing so, flip off "freestanding" mode for the cortex-m4f compiler's
use of libstdc++.
This is because some libraries appear to have been using STL headers
that cannot be safely linked against in freestanding mode (e.g.,
<ostream>). I am unsure why the prior compiler was not catching this.
If this becomes a problem, we can disable it.

Change-Id: Ie08ce2c089f787b0433a761ad2242dcd2a516404
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/motors/button_board.cc b/motors/button_board.cc
index fb17328..1d20fdb 100644
--- a/motors/button_board.cc
+++ b/motors/button_board.cc
@@ -289,7 +289,11 @@
   PORTB_PCR19 = PORT_PCR_DSE | PORT_PCR_MUX(2);
 
   // .1ms filter time.
-  PORTA_DFWR = PORTB_DFWR = PORTC_DFWR = PORTD_DFWR = PORTE_DFWR = 6000;
+  PORTA_DFWR = 6000;
+  PORTB_DFWR = 6000;
+  PORTC_DFWR = 6000;
+  PORTD_DFWR = 6000;
+  PORTE_DFWR = 6000;
 
   // Set up the buttons. The LEDs pull them up to 5V, so the Teensy needs to not
   // be set to pull up.