python3: fix build on native FreeBSD

* Make use of libxcrypt conditional (documented inline)
* Patch use of uname to to not pull in some impure information
* Various cases where behavior is split out among operating systems are
  now inclusive of FreeBSD

pkgs/development/interpreters/python/cpython/default.nix

@@ -121,6 +121,9 @@ let
     versionOlder
   ;
 
+  # mixes libc and libxcrypt headers and libs and causes segfaults on importing crypt
+  libxcrypt = if stdenv.hostPlatform.isFreeBSD then null else inputs.libxcrypt;
+
   buildPackages = pkgsBuildHost;
   inherit (passthru) pythonOnBuildForHost;
 
@@ -261,6 +264,7 @@ let
 
     multiarch =
       if isDarwin then "darwin"
+      else if isFreeBSD then ""
       else if isWindows then ""
       else "${multiarchCpu}-${machdep}-${pythonAbiName}";
 
@@ -445,7 +449,11 @@ in with passthru; stdenv.mkDerivation (finalAttrs: {
     "LDFLAGS=-static"
   ];
 
-  preConfigure = optionalString (pythonOlder "3.12") ''
+  preConfigure = ''
+    # Attempt to purify some of the host info collection
+    sed -E -i -e 's/uname -r/echo/g' -e 's/uname -n/echo nixpkgs/g' config.guess
+    sed -E -i -e 's/uname -r/echo/g' -e 's/uname -n/echo nixpkgs/g' configure
+  '' + optionalString (pythonOlder "3.12") ''
     # Improve purity
     for path in /usr /sw /opt /pkg; do
       substituteInPlace ./setup.py --replace-warn $path /no-such-path
@@ -476,10 +484,10 @@ in with passthru; stdenv.mkDerivation (finalAttrs: {
   postInstall = let
     # References *not* to nuke from (sys)config files
     keep-references = concatMapStringsSep " " (val: "-e ${val}") ([
-      (placeholder "out") libxcrypt
-    ] ++ optionals tzdataSupport [
-      tzdata
-    ]);
+      (placeholder "out")
+    ] ++ lib.optional (libxcrypt != null) libxcrypt
+      ++ lib.optional tzdataSupport tzdata
+    );
   in lib.optionalString enableFramework ''
     for dir in include lib share; do
       ln -s $out/Library/Frameworks/Python.framework/Versions/Current/$dir $out/$dir
@@ -661,7 +669,7 @@ in with passthru; stdenv.mkDerivation (finalAttrs: {
     '';
     license = licenses.psfl;
     pkgConfigModules = [ "python3" ];
-    platforms = platforms.linux ++ platforms.darwin ++ platforms.windows;
+    platforms = platforms.linux ++ platforms.darwin ++ platforms.windows ++ platforms.freebsd;
     mainProgram = executable;
   };
 })