misc pkgs: Remove unneeded *Platform == *Platform comparisons

PR #26007 used these to avoid causing a mass rebuild. Now that we know
things work, we do that to clean up.

pkgs/os-specific/linux/busybox/default.nix

@@ -63,7 +63,7 @@ stdenv.mkDerivation rec {
     CONFIG_DEFAULT_SETFONT_DIR "/etc/kbd"
 
     ${extraConfig}
-    $extraCrossConfig
+    CONFIG_CROSS_COMPILER_PREFIX "${stdenv.cc.prefix}"
     EOF
 
     make oldconfig
@@ -79,10 +79,6 @@ stdenv.mkDerivation rec {
 
   buildInputs = lib.optionals (enableStatic && !useMusl) [ stdenv.cc.libc stdenv.cc.libc.static ];
 
-  extraCrossConfig = if hostPlatform == buildPlatform then null else ''
-    CONFIG_CROSS_COMPILER_PREFIX "${stdenv.cc.prefix}"
-  '';
-
   enableParallelBuilding = true;
 
   meta = with stdenv.lib; {