zig cc: integration with sysroot arg (#10568)

Prior to this change, even if the use specified the sysroot on the
compiler line like so

```
zig cc --sysroot=/path/to/sdk
```

it would only be used as a prefix to include paths and not as a prefix
for `zig ld` linker.

src/clang_options_data.zig

@@ -1983,7 +1983,7 @@ flagpsl("MT"),
 .{
     .name = "sysroot",
     .syntax = .separate,
-    .zig_equivalent = .other,
+    .zig_equivalent = .sysroot,
     .pd1 = false,
     .pd2 = true,
     .psl = false,
@@ -5970,7 +5970,7 @@ jspd1("undefined"),
 .{
     .name = "sysroot=",
     .syntax = .joined,
-    .zig_equivalent = .other,
+    .zig_equivalent = .sysroot,
     .pd1 = false,
     .pd2 = true,
     .psl = false,

src/main.zig

@@ -1468,6 +1468,9 @@ fn buildOutputType(
                             fatal("expected [command|reactor] for -mexec-mode=[value], found '{s}'", .{it.only_arg});
                         };
                     },
+                    .sysroot => {
+                        sysroot = it.only_arg;
+                    },
                 }
             }
             // Parse linker args.
@@ -4115,6 +4118,7 @@ pub const ClangArgIterator = struct {
         strip,
         exec_model,
         emit_llvm,
+        sysroot,
     };
 
     const Args = struct {

tools/update_clang_options.zig

@@ -412,6 +412,10 @@ const known_options = [_]KnownOpt{
         .name = "emit-llvm",
         .ident = "emit_llvm",
     },
+    .{
+        .name = "sysroot",
+        .ident = "sysroot",
+    },
 };
 
 const blacklisted_options = [_][]const u8{};