Add Linear ASM compiler

[Freed-Wu]

Fix #13670

PS:

• same feature for cmake
• feature request for xmake

[Freed-Wu]

Now it works for me 😄

[dcbaker]

This deserves a release snippet, otherwise this all looks good to me.

[Freed-Wu]

What is a release snippet?

BTW, I use name TILinearAsmCompiler for *.sa. because cmake want to use ASM_LINEAR.

Currently, only c6000 support linear assemble *.sa. see cl6x --help | grep linear asm can find it.
other TI compilers for chip cl2000, cl430, armcl, tiarmcl don't support it. so we check it in sanity_check()

[dcbaker]

A release snippet is a small markdown description of the feature that will be put into the release notes when we cut 1.7.0, they go in docs/markdown/snippets, you can look at the existing snippets to see what they should look like.

[Freed-Wu]

Any other problem? I have tested this PR in this project and it can work.

[dcbaker]

With Eli's comments addressed this looks good to me.

my comments have been addressed now