w3nco %oneapi cflags: append -Wno-error=implicit-function-declaration (#43628)

* w3nco %oneapi cflags: append -Wno-error=implicit-function-declaration

* update flag for %apple-clang, %clang

* [@spackbot] updating style on behalf of eugeneswalker

var/spack/repos/builtin/packages/w3nco/package.py

@@ -19,3 +19,13 @@ class W3nco(CMakePackage):
     maintainers("t-brown", "AlexanderRichert-NOAA", "Hang-Lei-NOAA", "edwardhartnett")
 
     version("2.4.1", sha256="48b06e0ea21d3d0fd5d5c4e7eb50b081402567c1bff6c4abf4fd4f3669070139")
+
+    def flag_handler(self, name, flags):
+        if name == "cflags":
+            if (
+                self.spec.satisfies("%oneapi")
+                or self.spec.satisfies("%apple-clang")
+                or self.spec.satisfies("%clang")
+            ):
+                flags.append("-Wno-error=implicit-function-declaration")
+        return (flags, None, None)