add additional toolchain options

[oliverlee]

cxxopts: flags used only for compiling C++ targets
conlyopts: flags used only for compiling C targets
dbg_compile_flags: flags used when compiling in dbg mode
opt_compile_flags: flags used when compiling in opt mode
opt_link_flags: flags used when linking in opt mode

[oliverlee]

I'm not sure why tests started failing with:

In file included from test/aarch64-none-elf/library.cpp:1:
test/aarch64-none-elf/library.h:1:10: fatal error: stdint.h: No such file or directory
    1 | #include <stdint.h>
      |          ^~~~~~~~~~

after adding additional options where the defaults don't change anything.

I changed include_std to default to True, which the tests seem to assume.

[hexdae]

Hey @oliverlee, sorry I have been heads down on @diodeinc this week, will review soon

[oliverlee]

No worries and thanks for the notice.

[hexdae]

This looks good to me, should we merge @oliverlee?

[oliverlee]

I think this PR should be okay. I've been using it in another project without issues.