Zig 0.14 support: Add .ARM.extab to generated ARM linker.ld scripts

[marnix]

Per ziglang/zig#22685 (comment), Zig 0.14 has enabled 'unwind tables' for ARM embedded (and most other platforms). Therefore it looks like we need to update tools/generate_linker_script.zig, as part of the upgrade to Zig 0.14 (being done on the current zig-master branch).

diff --git a/tools/generate_linker_script.zig b/tools/generate_linker_script.zig
index 308b055e51..775892c0f6 100644
--- a/tools/generate_linker_script.zig
+++ b/tools/generate_linker_script.zig
@@ -107,6 +107,10 @@
 
         switch (program_args.cpu_arch) {
             .arm, .thumb => try writer.writeAll(
+                \\  .ARM.extab : {
+                \\      *(.ARM.extab* .gnu.linkonce.armextab.*)
+                \\  } >flash0
+                \\  
                 \\  .ARM.exidx : {
                 \\      *(.ARM.exidx* .gnu.linkonce.armexidx.*)
                 \\  } >flash0

I have no idea whether the above is actually correct, but it seems to work for me. (At the time of writing, I did not try to actually debug and look at any stack traces yet...)

I have no idea whether something similar would be needed for RISCV, and/or for other embedded platforms.

[marnix]

Actually this change can of course already be made on current master (see #373), but it's needed for Zig 0.14.