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/development/libraries/glew/1.10.nix

@@ -38,8 +38,8 @@ stdenv.mkDerivation rec {
     cp -r README.txt LICENSE.txt doc $out/share/doc/glew
   '';
 
-  makeFlags = if hostPlatform == buildPlatform then null else [
-    "SYSTEM=${if hostPlatform.isMinGW then "mingw" else hostPlatform.parsed.kernel}"
+  makeFlags = [
+    "SYSTEM=${if hostPlatform.isMinGW then "mingw" else hostPlatform.parsed.kernel.name}"
   ];
 
   meta = with stdenv.lib; {

pkgs/development/libraries/glew/default.nix

@@ -39,8 +39,8 @@ stdenv.mkDerivation rec {
     rm $out/lib/*.a
   '';
 
-  makeFlags = if hostPlatform == buildPlatform then null else [
-    "SYSTEM=${if hostPlatform.isMinGW then "mingw" else hostPlatform.parsed.kernel}"
+  makeFlags = [
+    "SYSTEM=${if hostPlatform.isMinGW then "mingw" else hostPlatform.parsed.kernel.name}"
   ];
 
   meta = with stdenv.lib; {

pkgs/development/libraries/libelf/default.nix

@@ -11,9 +11,8 @@ stdenv.mkDerivation rec {
     sha256 = "0vf7s9dwk2xkmhb79aigqm0x0yfbw1j0b9ksm51207qwr179n6jr";
   };
 
-  # TODO(@Ericson2314) Make unconditional next hash break
-  patches = if hostPlatform == buildPlatform then null else [
-    ./cross-ar.patch
+  patches = [
+    ./dont-hardcode-ar.patch
   ];
 
   doCheck = true;

pkgs/development/libraries/zlib/default.nix

@@ -4,10 +4,9 @@
 , static ? false
 }:
 
-let version = "1.2.11"; in
-
 stdenv.mkDerivation rec {
   name = "zlib-${version}";
+  version = "1.2.11";
 
   src = fetchurl {
     urls =
@@ -19,7 +18,7 @@ stdenv.mkDerivation rec {
 
   patches = stdenv.lib.optional hostPlatform.isCygwin ./disable-cygwin-widechar.patch;
 
-  postPatch = stdenv.lib.optionalString stdenv.isDarwin ''
+  postPatch = stdenv.lib.optionalString hostPlatform.isDarwin ''
     substituteInPlace configure \
       --replace '/usr/bin/libtool' 'ar' \
       --replace 'AR="libtool"' 'AR="ar"' \
@@ -30,14 +29,6 @@ stdenv.mkDerivation rec {
   setOutputFlags = false;
   outputDoc = "dev"; # single tiny man3 page
 
-  # TODO(@Dridus) CC set by cc-wrapper setup-hook, so just empty out the preConfigure script when cross building, but leave the old incorrect script when not
-  # cross building to avoid hash breakage. Once hash breakage is acceptable, remove preConfigure entirely.
-  preConfigure = stdenv.lib.optionalString (hostPlatform == buildPlatform) ''
-    if test -n "$crossConfig"; then
-      export CC=$crossConfig-gcc
-    fi
-  '';
-
   # FIXME needs gcc 4.9 in bootstrap tools
   hardeningDisable = [ "stackprotector" ];
 
@@ -49,37 +40,42 @@ stdenv.mkDerivation rec {
     # jww (2015-01-06): Sometimes this library install as a .so, even on
     # Darwin; others time it installs as a .dylib.  I haven't yet figured out
     # what causes this difference.
-  + stdenv.lib.optionalString stdenv.isDarwin ''
+  + stdenv.lib.optionalString hostPlatform.isDarwin ''
     for file in $out/lib/*.so* $out/lib/*.dylib* ; do
       install_name_tool -id "$file" $file
     done
+  ''
+    # Non-typical naming confuses libtool which then refuses to use zlib's DLL
+    # in some cases, e.g. when compiling libpng.
+  + stdenv.lib.optionalString (hostPlatform.libc == "msvcrt") ''
+    ln -s zlib1.dll $out/bin/libz.dll
   '';
 
   # As zlib takes part in the stdenv building, we don't want references
   # to the bootstrap-tools libgcc (as uses to happen on arm/mips)
-  NIX_CFLAGS_COMPILE = stdenv.lib.optionalString (!stdenv.isDarwin) "-static-libgcc";
+  NIX_CFLAGS_COMPILE = stdenv.lib.optionalString (!hostPlatform.isDarwin) "-static-libgcc";
 
-  crossAttrs = {
-    dontStrip = static;
-    configurePlatforms = [];
-  } // stdenv.lib.optionalAttrs (hostPlatform.libc == "msvcrt") {
-    installFlags = [
-      "BINARY_PATH=$(out)/bin"
-      "INCLUDE_PATH=$(dev)/include"
-      "LIBRARY_PATH=$(out)/lib"
-    ];
-    makeFlags = [
-      "-f" "win32/Makefile.gcc"
-      "PREFIX=${stdenv.cc.prefix}"
-    ] ++ stdenv.lib.optional (!static) "SHARED_MODE=1";
+  dontStrip = hostPlatform != buildPlatform && static;
+  configurePlatforms = [];
 
-    # Non-typical naming confuses libtool which then refuses to use zlib's DLL
-    # in some cases, e.g. when compiling libpng.
-    postInstall = postInstall + "ln -s zlib1.dll $out/bin/libz.dll";
+  installFlags = stdenv.lib.optionals (hostPlatform.libc == "msvcrt") [
+    "BINARY_PATH=$(out)/bin"
+    "INCLUDE_PATH=$(dev)/include"
+    "LIBRARY_PATH=$(out)/lib"
+  ];
+
+  makeFlags = [
+    "PREFIX=${stdenv.cc.prefix}"
+  ] ++ stdenv.lib.optionals (hostPlatform.libc == "msvcrt") [
+    "-f" "win32/Makefile.gcc"
+  ] ++ stdenv.lib.optionals (!static) [
+    "SHARED_MODE=1"
+  ];
+
+  passthru = {
+    inherit version;
   };
 
-  passthru.version = version;
-
   meta = with stdenv.lib; {
     description = "Lossless data-compression library";
     license = licenses.zlib;