perl: CompilerLexer: add -Wno-register to fix build with clang (#386081)

pkgs/top-level/perl-packages.nix

···
     };
     nativeBuildInputs = [ pkgs.ld-is-cc-hook ];
     buildInputs = [ ModuleBuildXSUtil ];
+    #  src/compiler/util/Compiler_double_charactor_operator.cpp:9:54: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
+    env = lib.optionalAttrs stdenv.cc.isClang {
+      NIX_CFLAGS_COMPILE = "-Wno-error=register";
+    };
     meta = {
       homepage = "https://github.com/goccy/p5-Compiler-Lexer";
       description = "Lexical Analyzer for Perl5";