`-fno-plt` disregarded when compiling *.zig

[xBZZZZ]

Zig Version

0.14.0-dev.2487+af89bb05d

Steps to Reproduce and Observed Behavior

1. create file plt_test.c with content:

   int imported_function(void);
   int exported_function(void){
   return imported_function()+1;
   }

2. run

   zig cc -target x86_64-linux-gnu -nostdlib -shared -Os -fno-plt -o plt_test_c.so plt_test.c

3. run

   eu-objdump --disassemble plt_test_c.so

   it outputs

   plt_test_c.so: elf64-elf_x86_64
   
   Disassembly of section .text:
   
       1314:    50                       push    %rax
       1315:    ff 15 c5 10 00 00        callq   *0x10c5(%rip)              # 0x23e0
       131b:    ff c0                    inc     %eax
       131d:    59                       pop     %rcx
       131e:    c3                       retq

   no .plt section because -fno-plt
4. create file plt_test.zig with content:

   extern fn imported_function() callconv(.C) i32;
   export fn exported_function() callconv(.C) i32{
   return imported_function()+1;
   }

5. run

   zig cc -target x86_64-linux-gnu -nostdlib -shared -Os -fno-plt -o plt_test_zig.so plt_test.zig

6. run

   eu-objdump --disassemble plt_test_zig.so

   it outputs

   plt_test_zig.so: elf64-elf_x86_64
   
   Disassembly of section .text:
   
       1314:    50                       push    %rax
       1315:    e8 16 00 00 00           callq   0x1330
       131a:    ff c0                    inc     %eax
       131c:    59                       pop     %rcx
       131d:    c3                       retq
   Disassembly of section .plt:
   
       1320:    ff 35 f2 10 00 00        pushq   0x10f2(%rip)               # 0x2418
       1326:    ff 25 f4 10 00 00        jmpq    *0x10f4(%rip)              # 0x2420
       132c:    0f 1f 40 00              nopl    0x0(%rax)
       1330:    ff 25 f2 10 00 00        jmpq    *0x10f2(%rip)              # 0x2428
       1336:    68 00 00 00 00           pushq   $0x0
       133b:    e9 e0 ff ff ff           jmpq    0x1320

   .plt section exists, -fno-plt disregarded

Expected Behavior

zig cc -target x86_64-linux-gnu -nostdlib -shared -Os -fno-plt -o plt_test_zig.so plt_test.zig

doesn't generate .plt section and

eu-objdump --disassemble plt_test_zig.so

outputs

plt_test_zig.so: elf64-elf_x86_64

Disassembly of section .text:

    1314:    50                       push    %rax
    1315:    ff 15 c5 10 00 00        callq   *0x10c5(%rip)              # 0x23e0
    131b:    ff c0                    inc     %eax
    131d:    59                       pop     %rcx
    131e:    c3                       retq

[alexrp]

This happens because we make no effort to handle this flag in the Zig driver; we just pass it through to Clang.

To support this option, we need to set this module flag: https://github.com/llvm/llvm-project/blob/9ee454a57c061e47223e079cdc64d315580367ed/llvm/lib/IR/Module.cpp#L717-L719