Or block with a build time if check does not build on Linux

[vlOd2]

Describe the bug

Compiling bug.v under Linux (or cross compiling from Windows) causes a build failure

Reproduction Steps

./v -g -o vdbg cmd/v && ./vdbg -os linux "bug.v" && "./bug"

fn my_erroring_function(_ int) !u32 {
	return error('!')
}

fn main() {
	x := my_erroring_function(1) or {
		$if !windows {
			panic(err)
		} $else {
			u32(0)
		}
	}
	println(x)
}

Expected Behavior

A successful build

Current Behavior

Cross compilation for Linux failed (first step, cc). Make sure you have clang installed.
builder error: ...\AppData\Local\Temp\v_0\bug.01KZ4EX56WSKGEY04ME1RTRMRT.tmp.c:4489:4: error: use of undeclared identifier '_t3'
 4489 |                         _t3 = builtin___v_panic(builtin__IError_str(err));
      |                         ^~~
...\AppData\Local\Temp\v_0\bug.01KZ4EX56WSKGEY04ME1RTRMRT.tmp.c:4494:3: error: use of undeclared identifier '_t3'
 4494 |                 _t3;
      |                 ^~~
2 errors generated.

Possible Solution

The V compiler seems to generate the following for the or block:

if (_t1.is_error) {
        IError _t2 = _t1.err;
        IError err = _t2;
        #if 1
            _t3 = builtin___v_panic(builtin__IError_str(err));
            VUNREACHABLE();
            ;
        #else
        #endif
        _t3;
    }

_t3 isn't declared anywhere, so it errors out (error: use of undeclared identifier '_t3')
but it doesn't even make sense to assign the result to a _t3 since it's a void function (probably why _t3 wasn't created)

Additional Information/Context

No response

V version

V 0.5.2 1cbcde2

Environment details (OS name and version, etc.)

|V full version      |V 0.5.2 0d38e8ad083e4e16058bfa5e2255d387e55ef2f0.1cbcde2
|:-------------------|:-------------------
|OS                  |windows,   
|Processor           |4 cpus, 64bit, little endian, N/A
|Memory              |7.74GB/15.95GB
|                    |
|V executable        |E:\SDK\vlang\v.exe
|V last modified time|2026-07-30 13:03:19
|                    |
|V home dir          |OK, value: E:\SDK\vlang
|VMODULES            |OK, value: ...\.vmodules
|VTMP                |OK, value: ...\AppData\Local\Temp\v_0
|Current working dir |OK, value: ...\Desktop\bug
|                    |
|Git version         |git version 2.53.0.windows.3
|V git status        |N/A
|.git/config present |false
|                    |
|cc version          |clang version 22.1.8 (https://github.com/llvm/llvm-project.git ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
|gcc version         |clang version 22.1.8 (https://github.com/llvm/llvm-project.git ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
|clang version       |clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
|msvc version        |N/A
|tcc version         |tcc version 0.9.28rc 2026-07-14_HEAD@d9d02c56* (x86_64 Windows)
|tcc git status      |thirdparty-windows-amd64 f7c7199b-dirty
|emcc version        |N/A
|glibc version       |N/A

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