kakasi: fix build with gcc15, modernize (#476841)

pkgs/by-name/ka/kakasi/package.nix

@@ -7,13 +7,39 @@
   libiconv,
 }:
 
-stdenv.mkDerivation rec {
+stdenv.mkDerivation (finalAttrs: {
   pname = "kakasi";
   version = "2.3.6";
 
+  src = fetchurl {
+    url = "http://kakasi.namazu.org/stable/kakasi-${finalAttrs.version}.tar.xz";
+    hash = "sha256-LuV7GwPHT9V2bnQcOBICjvxzvA4L+Tpuf/IOtHAfPuM=";
+  };
+
+  patches = [
+    (fetchpatch {
+      url = "https://src.fedoraproject.org/rpms/kakasi/raw/4756771/f/kakasi-configure-c99.patch";
+      hash = "sha256-XPIp/+AR6K84lv606aRHPQwia/1K3rt/7KSo0V0ZQ5o=";
+    })
+    ./gettext-0.25.patch
+  ];
+
   nativeBuildInputs = [ autoreconfHook ];
   buildInputs = lib.optionals stdenv.hostPlatform.isDarwin [ libiconv ];
 
+  env = lib.optionalAttrs (!stdenv.cc.isClang) {
+    NIX_CFLAGS_COMPILE = "-std=gnu17";
+  };
+
+  postPatch = ''
+    for a in tests/kakasi-* ; do
+      substituteInPlace $a \
+        --replace-quiet "/bin/echo" echo
+    done
+  '';
+
+  doCheck = false; # fails 1 of 6 tests
+
   meta = {
     description = "Kanji Kana Simple Inverter";
     longDescription = ''
@@ -25,27 +51,4 @@ stdenv.mkDerivation rec {
     license = lib.licenses.gpl2Plus;
     platforms = lib.platforms.unix;
   };
-
-  src = fetchurl {
-    url = "http://kakasi.namazu.org/stable/kakasi-${version}.tar.xz";
-    sha256 = "1qry3xqb83pjgxp3my8b1sy77z4f0893h73ldrvdaky70cdppr9f";
-  };
-
-  patches = [
-    (fetchpatch {
-      url = "https://src.fedoraproject.org/rpms/kakasi/raw/4756771/f/kakasi-configure-c99.patch";
-      hash = "sha256-XPIp/+AR6K84lv606aRHPQwia/1K3rt/7KSo0V0ZQ5o=";
-    })
-    ./gettext-0.25.patch
-  ];
-
-  postPatch = ''
-    for a in tests/kakasi-* ; do
-      substituteInPlace $a \
-        --replace-quiet "/bin/echo" echo
-    done
-  '';
-
-  doCheck = false; # fails 1 of 6 tests
-
-}
+})