stage2: implement noinline fn

[nektro]

Fixes #11767

test {
    foo();
}

noinline fn foo() void {
    //
}

[meg@nixos:~/dev/zig]$ ./zig-out/bin/zig ast-check -t test.zig 
# Source bytes:       55B
# Tokens:             16 (104B)
# AST Nodes:          9 (237B)
# Total ZIR bytes:    398B
# Instructions:       15 (135B)
# String Table Bytes: 7B
# Extra Data Items:   48 (192B)
%0 = extended(struct_decl(parent, Auto, {
  test line(0) hash(53b4e586ab7c73d53a2fda7c58ad19aa): %1 = block_inline({
    %9 = func_fancy(test, inferror, body={
      %2 = dbg_block_begin())
      %3 = dbg_stmt(2, 5)
      %4 = decl_val("foo") token_offset:2:5 to :2:8
      %5 = dbg_stmt(2, 8)
      %7 = dbg_block_end())
      %6 = call(nodiscard .auto, %4, []) node_offset:2:5 to :2:10
      %8 = ret_tok(@Zir.Inst.Ref.void_value) token_offset:3:1 to :3:2
    }) (lbrace=1:6,rbrace=3:1) node_offset:1:1 to :1:5
    %10 = break_inline(%1, %9)
  }) node_offset:1:1 to :1:5
  [40] foo line(4) hash(f3339e121db838fc9d98c7412345a9c5): %11 = block_inline({
    %13 = func_fancy(noinline, body={
      %12 = ret_tok(@Zir.Inst.Ref.void_value) token_offset:7:1 to :7:2
    }) (lbrace=1:24,rbrace=3:1) node_offset:5:1 to :5:12
    %14 = break_inline(%11, %13)
  }) node_offset:5:1 to :5:23
}, {}, {})

<snip>

; Function Attrs: noinline nounwind
define internal fastcc void @test.foo() unnamed_addr #0 !dbg !4183 {
Entry:
  ret void
}

<snip>

Full .ll log: https://clbin.com/ztvi5

[ghost]

Can it also handle this?

pub fn main() void {
    x();
}

noinline fn x() callconv(.Inline) void {}

I think it should be an error because it's ambiguous. In stage1 it's

broken LLVM module found: Attributes 'noinline and alwaysinline' are incompatible!
void ()* @x

This is a bug in the Zig compiler.thread 29374 panic:
Unable to dump stack trace: debug info stripped
Aborted (core dumped)

And we might also want to check other possibly problematic calling conventions in std.builtin.CallingConvention but I don't see any other apart from .Inline.

[nektro]

good catch, ill fix both notes and re-push