treewide: Remove stdenv.isCross

I *want* cross-specific overrides to be verbose, so I rather not have
this shorthand. This makes the syntactic overhead more proportional to
the maintainence cost. Hopefully this pushes people towards fewer
conditionals and more abstractions.

pkgs/development/libraries/libgcrypt/default.nix

···
     ++ stdenv.lib.optional stdenv.isDarwin gettext
     ++ stdenv.lib.optional enableCapabilities libcap;
 
-  preConfigure = stdenv.lib.optionalString stdenv.isCross ''
+  preConfigure = stdenv.lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) ''
     # This is intentional: gpg-error-config is a shell script that will work during the build
     mkdir -p "$NIX_BUILD_TOP"/bin
     ln -s ${libgpgerror.dev}/bin/gpg-error-config "$NIX_BUILD_TOP/bin"

pkgs/development/tools/build-managers/meson/default.nix

···
-{ lib, python3Packages, stdenv, targetPlatform, writeTextDir, substituteAll }: let
-  targetPrefix = lib.optionalString stdenv.isCross
-                   (targetPlatform.config + "-");
-in python3Packages.buildPythonApplication rec {
+{ lib, python3Packages, stdenv, targetPlatform, writeTextDir, substituteAll }:
+
+python3Packages.buildPythonApplication rec {
   version = "0.46.1";
   pname = "meson";
 
···
 
   crossFile = writeTextDir "cross-file.conf" ''
     [binaries]
-    c = '${targetPrefix}cc'
-    cpp = '${targetPrefix}c++'
-    ar = '${targetPrefix}ar'
-    strip = '${targetPrefix}strip'
+    c = '${stdenv.cc.targetPrefix}cc'
+    cpp = '${stdenv.cc.targetPrefix}c++'
+    ar = '${stdenv.cc.bintools.targetPrefix}ar'
+    strip = '${stdenv.cc.bintools.targetPrefix}strip'
     pkgconfig = 'pkg-config'
 
     [properties]
···
   # checkInputs = [ ninja pkgconfig ];
   # checkPhase = "python ./run_project_tests.py";
 
-  inherit (stdenv) cc isCross;
+  inherit (stdenv) cc;
+
+  isCross = stdenv.buildPlatform != stdenv.hostPlatform;
 
   meta = with lib; {
     homepage = http://mesonbuild.com;

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

···
 , pkgconfig, which
 , flex, bison
 , linuxHeaders ? stdenv.cc.libc.linuxHeaders
-, python
 , gawk
-, perl
+, withPerl ? stdenv.hostPlatform == stdenv.buildPlatform && perl.meta.available or false, perl
+, withPython ? stdenv.hostPlatform == stdenv.buildPlatform && python.meta.available or false, python
 , swig
 , ncurses
 , pam
···
       perl
     ];
 
-    buildInputs = stdenv.lib.optionals (!stdenv.isCross) [
-      perl
-      python
-    ];
+    buildInputs = []
+      ++ stdenv.lib.optional withPerl perl
+      ++ stdenv.lib.optional withPython python;
 
     # required to build apparmor-parser
     dontDisableStatic = true;
···
 
     postPatch = "cd ./libraries/libapparmor";
     # https://gitlab.com/apparmor/apparmor/issues/1
-    configureFlags = stdenv.lib.optionalString (!stdenv.isCross) "--with-python --with-perl";
+    configureFlags = [
+      (stdenv.lib.withFeature withPerl "perl")
+      (stdenv.lib.withFeature withPython "python")
+    ];
 
-    outputs = if stdenv.isCross then [ "out" ] else [ "out" "python" ];
+    outputs = [ "out" ] ++ stdenv.lib.optional withPython "python";
 
-    postInstall = stdenv.lib.optionalString (!stdenv.isCross) ''
+    postInstall = stdenv.lib.optionalString withPython ''
       mkdir -p $python/lib
       mv $out/lib/python* $python/lib/
     '';
···
 
     inherit doCheck;
 
-    meta = apparmor-meta "user-land utilities";
+    meta = apparmor-meta "user-land utilities" // {
+      broken = !(withPython && withPerl);
+    };
   };
 
   apparmor-bin-utils = stdenv.mkDerivation {

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

···
   ] ++ stdenv.lib.optional (!stdenv.hostPlatform.isMusl) libidn;
 
   # ninfod probably could build on cross, but the Makefile doesn't pass --host etc to the sub configure...
-  buildFlags = "man all" + stdenv.lib.optionalString (!stdenv.isCross) " ninfod";
+  buildFlags = "man all" + stdenv.lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) " ninfod";
 
   installPhase =
     ''

pkgs/stdenv/generic/default.nix

···
       inherit overrides;
 
       inherit cc;
-
-      isCross = targetPlatform != buildPlatform;
     }
 
     # Propagate any extra attributes.  For instance, we use this to

pkgs/tools/compression/lzip/default.nix

···
     sha256 = "0319q59kb8g324wnj7xzbr7vvlx5bcs13lr34j0zb3kqlyjq2fy9";
   };
 
-  configureFlags = "CPPFLAGS=-DNDEBUG CFLAGS=-O3 CXXFLAGS=-O3" + stdenv.lib.optionalString stdenv.isCross " CXX=${stdenv.cc.targetPrefix}c++";
+  configureFlags = [
+    "CPPFLAGS=-DNDEBUG"
+    "CFLAGS=-O3"
+    "CXXFLAGS=-O3"
+  ] ++ stdenv.lib.optional (stdenv.hostPlatform != stdenv.buildPlatform)
+    "CXX=${stdenv.cc.targetPrefix}c++";
 
   setupHook = ./lzip-setup-hook.sh;
 

pkgs/tools/system/monit/default.nix

···
-{stdenv, fetchurl, openssl, bison, flex, pam, zlib, usePAM ? stdenv.isLinux
- , buildPlatform, hostPlatform }:
-let useSSL = (openssl != null);
-    isCross = ( buildPlatform != hostPlatform ) ; in
+{ stdenv
+, fetchurl, bison, flex
+, zlib
+, usePAM ? stdenv.hostPlatform.isLinux, pam
+, useSSL ? true, openssl
+}:
+
 stdenv.mkDerivation rec {
   name = "monit-5.25.2";
 
···
     stdenv.lib.optionals useSSL [ openssl ] ++
     stdenv.lib.optionals usePAM [ pam ];
 
-  configureFlags =
-    if useSSL then [
+  configureFlags = [
+    (stdenv.lib.withFeature usePAM "pam")
+  ] ++ (if useSSL then [
       "--with-ssl-incl-dir=${openssl.dev}/include"
       "--with-ssl-lib-dir=${openssl.out}/lib"
-    ] else [ "--without-ssl" ] ++
-    stdenv.lib.optionals (! usePAM) [ "--without-pam" ] ++
+    ] else [
+      "--without-ssl"
+  ]) ++ stdenv.lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
     # will need to check both these are true for musl
-    stdenv.lib.optionals isCross [ "libmonit_cv_setjmp_available=yes"
-                                   "libmonit_cv_vsnprintf_c99_conformant=yes"];
+    "libmonit_cv_setjmp_available=yes"
+    "libmonit_cv_vsnprintf_c99_conformant=yes"
+  ];
 
   meta = {
     homepage = http://mmonit.com/monit/;