musl: deal with zig rename of i386 to x86

musl uses "i386" for this while Zig has switched to "x86".

src/Compilation.zig

@@ -4918,7 +4918,7 @@ fn detectLibCFromBuilding(
             const generic_name = target_util.libCGenericName(target);
             // Some architectures are handled by the same set of headers.
             const arch_name = if (target.abi.isMusl())
-                musl.archName(target.cpu.arch)
+                musl.archNameHeaders(target.cpu.arch)
             else if (target.cpu.arch.isThumb())
                 // ARM headers are valid for Thumb too.
                 switch (target.cpu.arch) {

src/musl.zig

@@ -258,7 +258,7 @@ pub fn buildCRTFile(comp: *Compilation, crt_file: CRTFile, prog_node: *std.Progr
     }
 }
 
-pub fn archName(arch: std.Target.Cpu.Arch) [:0]const u8 {
+fn archName(arch: std.Target.Cpu.Arch) [:0]const u8 {
     switch (arch) {
         .aarch64, .aarch64_be => return "aarch64",
         .arm, .armeb, .thumb, .thumbeb => return "arm",
@@ -275,6 +275,13 @@ pub fn archName(arch: std.Target.Cpu.Arch) [:0]const u8 {
     }
 }
 
+pub fn archNameHeaders(arch: std.Target.Cpu.Arch) [:0]const u8 {
+    return switch (arch) {
+        .x86 => return "x86",
+        else => archName(arch),
+    };
+}
+
 // Return true if musl has arch-specific crti/crtn sources.
 // See lib/libc/musl/crt/ARCH/crt?.s .
 pub fn needsCrtiCrtn(target: std.Target) bool {
@@ -361,7 +368,9 @@ fn addCcArgs(
     const target = comp.getTarget();
     const arch_name = archName(target.cpu.arch);
     const os_name = @tagName(target.os.tag);
-    const triple = try std.fmt.allocPrint(arena, "{s}-{s}-musl", .{ arch_name, os_name });
+    const triple = try std.fmt.allocPrint(arena, "{s}-{s}-musl", .{
+        archNameHeaders(target.cpu.arch), os_name,
+    });
     const o_arg = if (want_O3) "-O3" else "-Os";
 
     try args.appendSlice(&[_][]const u8{

src/wasi_libc.zig

@@ -256,7 +256,7 @@ fn addCCArgs(
     want_O3: bool,
 ) error{OutOfMemory}!void {
     const target = comp.getTarget();
-    const arch_name = musl.archName(target.cpu.arch);
+    const arch_name = musl.archNameHeaders(target.cpu.arch);
     const os_name = @tagName(target.os.tag);
     const triple = try std.fmt.allocPrint(arena, "{s}-{s}-musl", .{ arch_name, os_name });
     const o_arg = if (want_O3) "-O3" else "-Os";

tools/process_headers.zig

@@ -208,7 +208,7 @@ const musl_targets = [_]LibCTarget{
         .abi = MultiAbi.musl,
     },
     LibCTarget{
-        .name = "x86",
+        .name = "i386",
         .arch = MultiArch{ .specific = .x86 },
         .abi = MultiAbi.musl,
     },