improve zig cc flag integration

[andrewrk]

Extracted from #4774; see #3089 for the original issue.

• llvm target triple vs zig target triple; llvm -mcpu vs zig -mcpu zig cc: parse -target and -mcpu/-march/-mtune flags according to clang #4911
• test it with building some projects
  • libsoundio (I had to disable -fprofile-arcs)
  • LuaJIT (native)
  • LuaJIT (aarch64-linux-musl) - undefined symbol: __divtf3
• specific special args
  • -MD, -MV, -MF
  • nostdinc and how it relates to the native target not needed
  • stack protector args not needed
  • -g
  • omit-frame-pointer not needed
  • -fsanitize
  • -m args affect cpu flags and -march=native zig cc: integration with -m flags #4912
  • linker script
  • passing args to the linker
    • -z
    • -Xlinker
    • --for-linker
  • -L
  • version script
  • subsystem
  • -F
  • -framework
  • optimization flags
• look at the list of generated options and determine if any more need to be detected

[andrewrk]

some linker flags to add support for:

warning: unsupported linker arg: -E

warning: unsupported linker arg: -O3

warning: unsupported linker arg: --gc-sections

warning: unsupported linker arg: -z
warning: unsupported linker arg: nodelete

warning: unsupported linker arg: -z
warning: unsupported linker arg: defs

warning: unsupported linker arg: -allow-shlib-undefined

warning: unsupported linker arg: --version-script
warning: unsupported linker arg: /home/andy/Downloads/llvm-project-10/llvm/build-release-aarch64/tools/remarks-shlib/Remarks.exports

[andrewrk]

This is done now; some stuff has been extracted into separate issues.