gcc.libgcc: compare host and target platforms, rathern than their triples

The rest of our gcc expression prepends "${targetPlatform.config}-"
to paths and binaries if `hostPlatform!=targetPlatform`.  The
`libgcc.nix` expression was using
'hostPlatform.config!=targetPlatform.config`, which caused it to
look in the wrong place when moving files.  This commit corrects that.

pkgs/development/compilers/gcc/common/libgcc.nix

@@ -36,7 +36,7 @@ lib.optionals (lib.versionAtLeast version "11.0")
 
 (let
   targetPlatformSlash =
-    if hostPlatform.config == targetPlatform.config
+    if hostPlatform == targetPlatform
     then ""
     else "${targetPlatform.config}/";
 
@@ -83,7 +83,7 @@ in
     lib.optionalString (!langC) ''
       rm -f $out/lib/libgcc_s.so*
     ''
-    + lib.optionalString (hostPlatform.config != targetPlatform.config) ''
+    + lib.optionalString (hostPlatform != targetPlatform) ''
       mkdir -p $lib/lib/
       ln -s ${targetPlatformSlash}lib $lib/lib
     ''